Which teacher qualities matter for students' academic achievement in Cambodia?

Under the implementation of Sustainable Development Goal 4, Cambodia government has actively implemented comprehensive education strategic reform to ensure inclusive and equitable quality education (MoEYS, 2015, 2019a, b). The SDGs emphasize improving the quality of education with relevant and effective learning outcomes, and Cambodia government is also working to improve learning outcomes at all levels by enhancing teacher quality in the context of the SDGs.

Studies find that teacher quality is the most important variable influencing students' achievements (Kent, 2004; Rivkin, Hanushek, & Kain, 2005; Wallace, 2009). To make the education system better, policymakers all over the world thus identify teacher quality as a major catalyst for student academic achievement (Gratz, 2009). And many countries, including Cambodia, have been making efforts to improve the various dimensions of teacher quality through institutional reforms. SDG target 4.c emphasizes the importance of teacher quality by referring to the supply of qualified teachers, but there is no shared understanding about who is a “qualified” teacher (UNESCO, 2024). In the SDG indicator, UNESCO defines teacher quality in two ways: a teacher who has the minimum academic qualifications, and a teacher who has fulfilled at least the minimum organized teacher-training requirements (UNESCO, 2024). Although SDG target 4.c covers both aspects, global indicator 4.c.1 – the proportion of teachers “with the minimum required qualifications” – measures the share of teachers with at least the minimum organized pedagogical teacher training required for teaching at the relevant level in each country (UNESCO, 2024).

While the minimum required academic qualifications for teachers vary by country, most countries provide teacher training at the higher education level, and UNESCO also suggests that teacher training should be provided at higher education institutions (UNESCO, 2015). However, in developing countries, teacher training is still provided at the secondary level or as a nondegree course, and in some cases, teacher training systems are not systematically functioning (UNESCO, 2015). In general, completion of a teacher training program is considered the main requirement to obtain a teaching qualification, but it can be the case that countries adjust such condition or allow teach without qualification in order to solve shortage of teachers (UNESCO, 2015). Therefore, in many countries, teachers are often qualified but untrained or trained but unqualified (UNESCO, 2024). Another issue related to teacher quality is that even if a teacher has teaching qualification, they may not have appropriate competencies in both subject matter knowledge and pedagogical knowledge. Teachers can improve their pedagogical skills through experience as a teacher in schools, even if they didn't receive sufficient training in a teacher training institution. In addition, teacher professional development (TPD) is considered the most effective way for teachers to continually improve their subject matter-related and pedagogical knowledge (Cohen & Hill, 1998; Desimone, 2009; Phin, 2014; Wenglinsky, 2000).

In this context, the Cambodian government has made significant efforts to improve teacher quality and increase outcomes of school through institutional improvements such as reforming the teacher education system and expanding TPD opportunities (MoYES, 2015, 2019a, b; UNESCO, 2015) such as upgrading two-year teacher training institutions into four-year colleges and raising the minimum educational qualifications for teachers or providing various professional development opportunities for in-service teachers (MoYES, 2019a, b).

Cambodia has made many efforts to improve teacher quality, but few studies have analyzed the relationship between teacher quality and students' academic achievement in the context of these policy efforts so far (Phin, 2014). As education policies can have varying effects depending on a country's social and economic context, it is unclear to what extent teacher quality can significantly impact the Cambodian education system. Therefore, it is crucial to determine how Cambodia's policy direction is specifically linked to the quality of teachers, as this is essential for the improvement of school education and its impact on student academic achievement.

Cambodia has established and implemented a national learning assessment system that evaluates the “quality of education” at the governance level through indicators of students' academic achievement (Bo, Seak, Sin, & Souk, 2019; Phin, 2014). However, recent reports show that despite the secondary education enrollment rate approaching nearly 100% since 2000 and the proportion of minimum qualified teachers reaching nearly 100% since 2013, students' academic performance has remained relatively low (UNESCO Institute for Statistics, 2025). In response, the Cambodian government has identified the enhancement of teacher quality as a key strategy for improving the quality of education and has been continuously implementing teacher-related policies since 2015. While similar approaches are being adopted in various developing countries, Cambodia is distinguished by its considerable educational potential and its notably strong commitment to advancing teacher policy and reform ^[1] (Bo et al., 2019).

In this context, this study examined the theoretically grounded positive relationship between teacher quality and students' academic achievement in Cambodia. Through this analysis, the study contributes to a deeper understanding of teacher quality and its theoretical associations within the frameworks of school effectiveness research and an integrated approach to teacher quality. It also offers evidence-based policy options for strengthening Cambodia's teacher education system. To achieve this, the study was guided by the following question:

• What kind of teacher quality affects students' academic achievement?

Teacher quality is one of the most important school-based determining factors contributing to student academic growth (Darling-Hammond & Berry, 2006; Harris & Sass, 2009). There is an assumption that teacher quality consists of teaching quality, or that teaching quality is an outcome of teacher quality. Therefore, teaching quality has two dimensions: the teaching task of teachers and the student achievement that teachers foster (Fenstermacher & Richardson, 2005; Goe, 2007, p. 8). In this study, we focused on the achievement of student learning that teachers can foster.

To assess the quality of teachers as a crucial catalyst in school education in Cambodia, this study is rooted in educational effectiveness research and seeks to explore the relationship between teacher quality focused on “teacher qualifications” at the school system level and students' academic achievement (Goe, 2007). Many definitions of teacher quality exist in the literature, and it encompasses various indicators in much empirical research. According to most related studies, two easily observable characteristics of teacher quality are teachers' educational background such as degree level and teaching experience or career (Boyd et al., 2006; Clotfelter, Ladd, & Vigdor, 2007; Hanushek, Kain, O'Brien, & Rivkin, 2005; Rivkin et al., 2005), and participation in TPD (Blömeke et al., 2015, p. 24; Strøm & Falch, 2020).

This study developed an integrated model of teacher quality that incorporates educational qualifications, teaching experience and participation in TPD – factors that have often been examined separately in previous research. This approach aims to prevent any single element, such as teaching experience, from being overly reduced to or substituted for the broader and more comprehensive concept of teacher quality. To design an integrated model of teacher quality, this study reviewed prior research on teacher educational qualifications, teaching experience and TPD, which have traditionally been examined as separate domains.

There are numerous debates regarding teacher quality, but everyone agrees that teacher qualification is a fundamental prerequisite. Darling-Hammond and Bransford (2007) define a well-qualified teacher as one who is fully certified and holds the equivalent of a major in the field being taught. Teacher qualification has been considered an essential factor that promotes the improvement of the school/classroom environment as well as students' educational achievement (Wallace, 2011). In most countries, the qualification and license to teach in schools must be obtained through formal educational qualifications. A qualified teacher is one who holds a teaching certificate and/or licensed by the state/nation’ owns at least a bachelor's degree from a tertiary education institution (Musau & Abere, 2015; Usman, 2012).

Many studies have demonstrated a positive association between teachers who are certified or qualified, holding a bachelor's degree according to national standards and students' learning outcomes (Akinsolu, 2010; Greenwald, Hedges, & Laine, 1996). According to Greenwald et al. (1996), a study frequently cited in educational effectiveness research, teacher education shows very strong relations with student achievement. Akinsolu (2010) reveals a positive correlation between teachers' qualifications and the academic performance of secondary education students in Osun State of Nigeria. However, using Sandiego of U.S student-teacher data, Betts, Zau, and Rice (2003, p. 112) asserted that teacher qualification does not always seem to matter. They found that factors such as the level of education of teachers appear to be more significant in the upper grades of secondary education than in the lower grades.

On the other hand, some studies argue that factors other than teachers' qualifications are more important (Kimani, Kara, & Njagi, 2013; Musau & Abere, 2015). A study examining the relationship between teachers' academic background and students' achievement in science, mathematics and technology subjects (Musau & Abere, 2015) found that teachers' qualifications accounted for only 0.1% of the variance in students' SMT subject achievements. And even with the same bachelor's degree, the “education specialization” can be crucial to teacher quality. According to Singh and Sarkar (2015), teacher's general bachelor's degree was unrelated to academic achievement, whereas an education-specific and/or professional bachelor's degree was associated with academic achievement. Goldhaber and Brewer (1997, p. 23) demonstrated that while teachers with a general bachelor's degree qualification were not statistically significant in relation to students' mathematics tests, teachers with a math-related bachelor's degree qualification were clearly associated with higher student scores on mathematics tests.

Seweje and Jegede (2005) stated that teaching quality is not derived only from one's academic background, but it is based upon pedagogical skill. Experience as a teacher in school can be the best way to gain outstanding pedagogical skill. Teaching experience, together with certification status, has often been used as a variable to proxies of teacher quality (Huang & Moon, 2009). Several studies have found out the strong positive associations between teachers' years of experience and student academic achievement (Clotfelter et al., 2007; Ladd, 2008). Hanushek (1986) concluded that there was no clear evidence that teaching experience positively affects students' achievement. Wiswall (2013) reported that students taught by teachers with more than 30 years of experience showed higher mathematics achievement compared to those taught by teachers with five years of experience. Papay and Kraft (2015) found that teachers with more years of experience have positive impacts on students' mathematics test scores. Stronge, Ward, Tucker, and Hindman (2007) and Kingsley and Omoregie (2021) all documented that there is positive correlation between experienced teachers and students' academic achievement assessment in Literacy, Mathematics, Social Studies and Science subject.

Although teachers' teaching experience plays a positive role in students' educational achievement, some studies have found that the effectiveness of teachers' experience diminishes or mitigates students' academic achievement (Canales & Maldonado, 2018; Chingos & Peterson, 2011; Ladd, 2008; Murnane, 1996; Othman & Senom, 2019; Shuls & Trivitt, 2015). According to Murnane (1996), the impact of teachers' experience on students' achievement improves rapidly during the first three years of a teaching career, peaks between the third and fifth years, but shows only a moderate contribution after five years. Several studies have also found a significant association between teaching experience and students' math achievement, suggesting that the effect of experience extends beyond the first few years of teaching (Canales & Maldonado, 2018; Othman & Senom, 2019). Chingos and Peterson (2011) reported that regarding student mathematics achievement, teachers generally become more effective with the first few years of teaching experience and provided evidence that teachers become less effective with more experience, particularly later in their careers.

Furthermore, some international or cross-country comparative studies have reported either no relationship or a negative relationship between teachers' teaching experience and students' academic achievement (Wößmann, 2003; Xin, Xu, & Tatsuoka, 2004). Xin et al. (2004) demonstrated that teachers' years of experience generally had no effect on either students' Mathematics or Science test scores in the East Asia countries. And Wößmann (2003) investigated that teachers' years of experience were negatively associated with student achievement.

Teacher qualification and experience influence student learning, but not consistently or strongly. Their impact on student learning achievement may weaken over time (Betts et al., 2003). The most effective way for teachers to continually improve their quality is through participation in TPD activities. Student achievement varies depending on the quantity or quality of the education/training for professional development that teachers receive (Desimone, 2009). Several studies indicate that certain types of professional development contribute to teacher quality and student achievement. Specifically, professional development that is sustained, aligned with the curriculum and focused on instruction is shown to positively influence school-level achievement in mathematics and science at high school levels (Cohen & Hill, 1998; Wenglinsky, 2000).

In the most of countries, a variety of TPD activities exist, from very short-term classes to comprehensive programs (Goldsmith, Doerr, & Lewis, 2014; Guskey, 2000; Quattlebaum, 2015). TPD includes school-based programs, coaching, seminars or other types of out- and in-service training with the aim of supporting the development of in-service teachers' competencies or abilities, such as instructional quality (Didion, Toste, & Filderman, 2020). To be considered, TPD could specifically include: (1) any session lasting one hour or longer; (2) delivery during vacations or school semesters; (3) delivery in the context of current educational practices or subject matter content; (4) whole-group meetings, short-term coursework, professional learning communities, ongoing coaching, online training and follow-up sessions and (5) delivery by school, district or university personnel.

Recently, some researchers conceptualized the collaboration-based TPD (Desimone, 2009; Goe, 2007). Representative examples of collaboration-based TPD include collaborative learning activities (Didion et al., 2020) and teacher-to-teacher mentoring (Goe, 2007). Engaging in TPD activities while participating in networks or teams of fellow teachers both within and outside the school is a key aspect of collaboration-based TPD. However, there are substantial discussions that high-quality TPD can improve teacher practices, less evidence exists for the effects of TPD on intermediate outcomes for student achievement (Wallace, 2009; Yoon, Duncan, Lee, Scarloss, & Shapley, 2007). According to Frome, Lasater, and Cooney (2005), the percentage of teachers participating in mentoring or induction programs is positively correlated with school-level achievement in mathematics. However, contrasting findings emerged from a study on rural schools in Brazil, where no beneficial relationship between TPD and student achievement was observed (Harbison & Hanushek, 1992). Harbison and Hanushek (1992) speculated that this result may be attributed to the targeting of particularly underqualified teachers for participation in the studied TPD programs.

We utilized Cambodian data from the published School-based PISA for Development (hereafter PISA-D). Programme for International Student Assessment for Development (PISA-D) set the goal to overcome barriers preventing low- and middle-income countries from engaging in PISA by introducing new proficiency levels at the lower end of the scale and anchoring PISA. PISA-D employs the same evaluation system as PISA but has been customized and supplemented for the context and environment of developing countries (OECD, 2019). The PISA-D survey includes school data, along with data on teachers and students within each school (OECD, 2019), indicating clustered/nested data. This feature provides an advantage for conducting multilevel analyses to explore school factors related to students' cognitive and affective achievements (Ho, 2013; OECD, 2009). In this study, we used merged data from three questionnaires: students, teachers and schools/principals. Cambodia's PISA-D total sample is composed of 5,162 students, 4,315 teachers and 170 schools. For this study, we focused on 15-year-old adolescents enrolled in general secondary education, selecting only public schools in Cambodia. The final sample for this study comprised 4,777 students, 4,085 teachers and 157 public schools in Cambodia.

We utilized students' academic achievement scores in Mathematics, Literacy and Science as dependent variables. PISA-D provides 10 plausible values (hereafter 10 PVs) for the cognitive domains. We used all plausible values of Mathematics, Literacy and Science scores provided by PISA-D. By repeatedly inputting the 10 PVs of students' academic achievement, we calculated the probability of parameter significance using the t-value derived from the mean of parameter estimates and the mean of standard errors.

Teacher educational qualification refers to the percentage of teachers whose highest educational attainment is above a bachelor's degree. Teaching experience refers to teachers' years of experience and is treated as a continuous variable from 1 to 45. To apply this variable at the school level, we calculated the mean teaching experience for each school. We utilized only two collaborative-based TPD items, two individual activity-based TPD items and two items related to general teacher training participation, all based on theoretical background (Desimone, 2009; Didion et al., 2020; Frome et al., 2005; Goe, 2007), among the 10 TPD items provided by TALIS. TPD1 (Participation in teachers' networks) refers to the percentage of teachers at the school level who have participated in a network specifically formed for the professional development of teachers in the last year. TPD2(Mentoring or peer observation) refers to the percentage of teachers at the school level who participated in mentoring, peer observation and coaching as part of a formal school arrangement in the last year. TPD3 (Reading books or materials) refers to the percentage of teachers at the school level who have engaged in reading professional literature, such as journals, evidence-based papers and thesis papers. TPD4 (Informal dialog with colleague) refers to the percentage of teachers at the school level who have engaged in informal dialogue with school colleagues on how to improve their teaching. TPD5 (Attending workshops on teaching methods) refers to the percentage of teachers at the school level who have attended courses or workshops focused on teaching methods. TPD6 (Attending workshops related to subject matters) refers to the percentage of teachers at the school level who have attended courses or workshops relevant to their subject-matter fields.

To alleviate selection bias and provide dependable information regarding the relationships between teacher quality and students' academic achievement, this study controlled for several significant covariates. And since we are interested in the quality of teachers at the school level, we considered more school-level control variables than student-level control variables.

First, we employed the population size of school's location, school size, school's basic infrastructure and the number of students per teacher as school-level control variables (Daly, Liou, & Der-Martirosian, 2021; Greenwald et al., 1996; Porfeli, Wang, Audette, McColl, & Algozzine, 2009; Wößmann, 2003). Location size is the population size of school's location. School size refers to the total number of students (girls and boys) in each school. Class size refers to the average size of class in each school. Basic infrastructure indicates the level of school resources.

Second, we employed students' gender and socio-economic status (SES) as student-level control variables (Byrnes, 2005; Broer, Bai, & Fonseca, 2019; Guiso, Monte, Sapienza, & Zingales, 2008; Wößmann, 2003).

Gender represents as a dummy variable, taking a value of 1 for female students and 2 for male students. The PISA index of Economic, social, and cultural status (ESCS) closely relates to other measures of socio-economic status provided by the PISA assessment (OECD, 2019). ESCS is a single composite score that combines financial, social, cultural and human-capital resources available to students.

In the ESCS variables at the student level, including location size, school size and class size at the school level, we found less than 1% missing data. To address these missing values, we conducted five rounds of multiple imputations and applied weights at the student level of the data provided by PISA-D. Table 1 presents detailed information on the variables included in the analysis.

Through school education, understanding the explanatory power of organizational dimensions in terms of cognitive and emotional competencies acquired by students, and identifying school factors, Hierarchical Linear Modeling (hereafter HLM) analysis is suitable (Raudenbush & Bryk, 2002). We used HLM to evaluate both the explanatory power of teacher quality at the school level in relation to variations in students' academic achievement and the effectiveness of teacher quality as a school factor affecting students' academic performance. Centering correction has the advantage of facilitating the interpretation of results in HLM and reducing multicollinearity among variables. In this study, we applied group mean centering at the student level, grand mean centering at the school level and did not apply centering correction for binary variables. To ensure that each sampled student and school represented the correct number of students and schools in the population, we used a student weight variable. For imputing missing data at the student and school level, we used five times multiple imputation. Before analyzing the research model, we conducted a basic model analysis to understand the explanatory power of individual and school factors on the academic achievement of Cambodian students and derived the values for the Intraclass Correlation Coefficient. We set our equations below and the research model in Figure 1.

[Basic model: Unconditional model]

To address our research question, we designed a research model of teacher quality while considering control variables. The research models represent full conditional models with variables introduced at level 1 and 2. The equations below define the research model.

[Research model: Intercepts and Slopes as Outcomes Model]

Where:

• $Yij=academicachievementofstudentiinschoolj$

• $β0j=jschoolaverageacademicachievement$

• $rij=variancebetweenstudents$

• $γ00=overallschoolaverageacademicachievement$

• $u0j=variancebetweenschools$

According to the basic model analysis of domain-specific achievements, it was evident that there were differences in all achievements among individual students and among schools. We calculated the Intra-Class Correlation values through the variance at the student and school levels. As a result, the percentage of variance explained at the student level for mathematics achievement was 73.05%, and at the school level was 26.95%. For reading achievement, the student level explained 76.08%, while the school level explained 23.92%. In the case of science achievement, the student level explained 77.85% and the school level explained 22.15%. Additionally, it was observed that the school-level explanation was highest for mathematics, followed by reading and science achievements. The results of the base model are presented in Table 2.

According to the results of the research model, school teachers' educational qualifications showed statistically significant associations with all academic achievements (Mathematics, β = 44.07, p < 0.001; Literacy, β = 35.26, p < 0.001; Science, β = 24.14, p < 0.01). Prior studies often interpret a 39-point gap in PISA scores as approximating one year of learning (Hanushek & Woessmann, 2011; OECD, 2010, p. 14). This result suggests that differences in the proportion of adequately qualified teachers across schools may lead to substantial learning gaps – equivalent to roughly half a year to a full year of schooling – between students in different schools.

However, teaching experience did not exhibit statistically significant associations with all academic achievements. Among the TPD variables, school teachers' participation in workshops or courses related to subject matter consequently promoted students' academic achievements (Mathematics, β = 55.72, p < 0.01; Literacy, β = 35.04, p < 0.01; Science, β = 29.77, p < 0.1). And school teachers' participating in mentoring or peer observation showed a statistically negative association with students' academic achievements (Literacy, β = −14.58, p < 0.1; Science, β = −13.20, p < 0.1).

Among the control variables, it was observed that students attending schools located in areas with a larger population tended to exhibit higher academic achievements (Mathematics, β = 8.35, p < 0.001; Literacy, β = 6.85, p < 0.001; Science, β = 4.34, p < 0.01). Additionally, students attending schools with large class sizes showed better academic achievement (Mathematics, β = 0.69, p < 0.001; Literacy, β = 0.45, p < 0.01; Science, β = 0.44, p < 0.01).

Among student-level control variables, gender-based disparities in academic achievement were observed only in reading, where female students (β = −15.32, p < 0.001) showed higher reading academic achievement. However, no significant gender differences in academic achievement were found in mathematics and science. The variable that can be referred to as a proxy for socio-economic status in this study, ESCS (Mathematics, β = 7.36, p < 0.001; Literacy, β = 3.08, p < 0.01; Science, β = 2.44, p < 0.01), influenced students' achievement. The results of the research model are presented in Table 3.

The findings indicate that teachers' educational qualifications show a significant positive relationship with students' academic achievement in Cambodia. SDG 4.c emphasizes the supply of qualified teachers for the achievement of SDG 4; a teaching qualification is suggested to be completion of higher education. The Cambodian government also made this condition mandatory relatively recently, in 2020 (UNESCO, 2015, 2024). Although Cambodia has reformed their teacher training systems by increasing the years of teacher education, there has been debate about whether this approach can lead to improved student learning outcomes (Phin, 2014). A previous study that compared the effects of family background and school policies on students' academic achievement in Asian countries such as Singapore, Thailand and Korea; it was found that in Asian countries, the educational qualifications of teachers had either insufficient or no significant association with students' academic achievement (Wößmann, 2003, p. 21). In addition, it has been suggested that a teacher's general university graduation qualification may be unrelated to students' academic achievements, and qualifications that enable the teaching of specific subjects or majors may be more crucial (Goldhaber & Brewer, 1997, p. 23; Singh & Sarkar, 2015). However, this research showed that the university graduation of Cambodian teachers could have a significant relationship with students' academic achievements. This result suggested that university graduation itself, regardless of the type of degree or major, can be understood as a proxy for teacher quality in Cambodia context. Teachers who have graduated from university have a longer learning time than those who have not and have more opportunities to acquire more specialized subject matter knowledge and pedagogical skills during this time. Therefore, it can be understood that the educational qualification of teachers has a significant association with students' academic achievement.

This study also showed that schools with more teachers participating in subject-matter TPD activities have higher students' academic achievement. Because TPD is considered the most effective way for teachers to acquire subject matter and pedagogical knowledge, Cambodian government has provided TPD activities such as short-term intensive training workshops, mentoring programs and peer-based support models (Phin, 2014). However, the result also showed no effect of TPD and a negative relationship between participation in a teachers' participating in mentoring or observation and student achievement. This result suggested the effect of TPD on student achievement could differ by the type of TPD activity in Cambodia context. As Harbison and Hanushek (1992) reported, there was no relationship between TPD and student achievement in rural schools in Brazil and discussed the quality of mentors; it is crucial who serve as mentors in mentoring and peer teacher scholarship programs. In addition, the quality of teachers involves various aspects of development and stages (Fenstermacher & Richardson, 2005; Yoon et al., 2007); there is a need to investigate how participation in these TPD activities affects various factors related to teacher professionalism.

In addition, when considering the practical context, the effectiveness of teachers' TPD activities is likely to emerge from the complex interactions among multiple layers of factors – teachers’ individual circumstances (such as job satisfaction and workload), the environmental conditions of the schools in which they work (including relationships with principals and colleagues) and the mode of delivery and quality of the TPD programs provided. Therefore, for specific TPD activities that showed negative associations, it is necessary to interpret the results in conjunction with mediating factors or contextual constraints that may hinder the positive effects of TPD.

Beyond the intrinsic features of TPD programs, particular attention should be paid to identifying how school-level structural and environmental constraints in Cambodia may have limited the effective functioning of specific TPD activities that exhibited negative associations with student achievement. A representative constraint is teachers' engagement in second jobs, which is one of the greatest barriers to continuous professional development for Cambodian teachers (CITA, 2013). Teachers' engagement in secondary employment may naturally lead to a diffusion of their professional focus, thereby reducing the time and energy that could otherwise be devoted to core instructional responsibilities. Due to structural limitations, Cambodian teachers receive low salaries and the government officially permits secondary employment; consequently, a considerable number of teachers undertake additional work to support their livelihoods. Although official statistics are not available, the PISA-D Cambodia data used in this study show that 61.9% of teachers engage in private tutoring and 33.5% participate in noneducational secondary jobs. These findings suggest that substantial socio-structural and economic constraints limit Cambodian teachers' ability to participate fully in TPD activities. To develop effective TPD systems in the future, it is essential to identify and address these constraints.

Teaching experience of teachers had no statistically significant effect on students' academic achievements. According to Seweje and Jegede (2005), teacher quality is based on pedagogical skills as well as academic qualifications, and experience as a teacher in school can be the best way to gain outstanding pedagogical skills. Therefore, many researchers have demonstrated that teaching experience has strong positive associations with student academic achievement (Clotfelter et al., 2007; Huang & Moon, 2009; Ladd, 2008). Other research indicated that the decisive aspects of teaching experience exist only in the initial five years and diminish over the long term (Chingos & Peterson, 2011; Canales & Maldonado, 2018; Ladd, 2008; Murnane, 1996; Othman & Senom, 2019; Shuls & Trivitt, 2015). However, we found that teachers' teaching experience was not related to students' academic achievement in Cambodia. This implies that the teaching experience in Cambodian schools does not lead to improved teacher professionalism influencing student academic achievements. Therefore, to improve the quality of teachers, it is necessary to provide more systematic and institutionalized opportunities to increase their professionalism, rather than simply relying on their teaching experience.

This study examined the relationship between teacher quality and students' academic achievement in Cambodia. The findings revealed that teachers' educational qualifications and subject matter–focused TPD were significantly and positively associated with student achievement, while teaching experience and other TPD activities were not statistically significant predictors. Therefore, for quality education to be more than just rhetoric but a tangible outcome in terms of improved academic achievement in Cambodia, it is necessary to train and deploy teachers with appropriate educational qualifications and provide them with TPD for continuous acquisition of subject knowledge.

Recent reforms in Cambodia's teacher education system have shifted the national focus from the quantitative goal of supplying qualified teachers to the qualitative goal of ensuring continuous professional development, particularly after 2019 (MoEYS, 2019b). Notably, the Master Plan for Teacher Qualification Upgrade 2021–2025 and the Strategic Plan for Teacher Education Reform 2024–2030 emphasize not only restructuring the teacher education system but also strengthening teachers' ongoing professional development and specialization.

The findings of this study suggest that, for Cambodia's teacher education reforms to be successful, it is crucial to go beyond improving qualification standards and revising career pathways. Addressing the structural constraints that hinder teachers' participation in TPD, as well as designing high-quality training programs that expand opportunities for continuous professional development, will be essential to enhancing teacher quality in a sustainable manner.

Despite these findings and implications, this study has several limitations.

First, however, this study has a limitation in that the variables used do not distinguish between types of education-related professional degrees or specific fields of specialization. Nevertheless, given the strong hierarchical significance of higher education credentials in the Cambodian context, university graduation can be reasonably interpreted as a proxy for teacher quality. That said, future research should employ more fine-grained measures that incorporate detailed information on education-related professional degrees and academic backgrounds in order to more precisely examine their associations with educational quality and student achievement.

Second, Teacher quality encompasses not only effective pedagogical expertise in delivering subject-area knowledge but also a diverse set of competencies and skills (Darling-Hammond & Berry, 2006; Wiswall, 2013). However, this study, with its focus on the quality of teachers directly related to the enhancement of students' academic achievement (Fenstermacher & Richardson, 2005), has limitations in exploring the power of TPD within this specific context. Because this study focuses primarily on teacher quality, unobserved contextual variables – such as school leadership or classroom-level instructional practices – may also have influenced the results. Therefore, future research should examine the structural relationships among school environments, teacher quality and student achievement to provide a more comprehensive understanding of these interconnected factors.

Also, we employed a greater number of controlled variables at the same school level and relatively fewer variables at the student level to design an appropriate and effective model focusing on the quality of teachers at the school level. The results of this study showed that school-level factors may be considered as more statistically significant predictors of students' academic achievement compared to factors such as family background or gender. However, this does not imply that the effects of individual or school-level factors on student outcomes are greater or smaller.

Finally, this study has limitations in establishing causal relationships between teacher quality and student achievement, as it employed a multilevel model using cross-sectional data. Future research should utilize repeated longitudinal data collected directly in Cambodia, as well as qualitative or mixed-methods approaches, to more clearly identify causal mechanisms and to further develop a contextualized theoretical understanding of teacher quality in Cambodia. These limitations are expected to be overcome through various follow-up studies.