Among over 200 Hattie performance indicators, teacher estimates of achievement, collective teacher efficacy, and teacher credibility are the highest effect size indicators, directly influenced by educators [1]. In major cities like Almaty and Astana, frequent teacher turnover is a continuous issue, due to increasing number of new schools each year, leading to competitive job market. While this dynamic contributes to economic benefits, it may also negatively affect the students’ academic performance. Therefore, this study examines the effect of subject teacher turnover on the quality of education.

           The research was carried out at the Nazarbayev Intellectual School of Chemistry and Biology in Almaty, prompted by frequent turnover in teaching staff and their impact on the results of external aggregate assessments.  The research hypothesis was that frequent subject teacher turnover can negatively affect the quality of education. A statistical analysis was conducted on 49 eleventh grade students to monitor teacher changes and academic performance. Additionally, an intervention was conducted, where geography teachers were changed for 55 eighth grade students and 52 tenth-grade students.

            Student survey results suggest that the age and gender of the teacher had not a significant the quality of education, and the length of service has a greater impact, while teaching experience and the frequency of teacher changes significantly affected learning outcomes. This study noted a lower academic performance in the first quarter of the academic year than in the same period of the previous year, but gradually increased in the following quarters, due to the adaptation period. Because of this, frequent (>2 in a year) teacher turnover negatively impacted short-term academic performance of the students. Data suggests that this negative effect can be mitigated by joint lesson planning among teachers.

            Since persistence of a single teacher can also lead to stagnation, we suggest long-term studies with larger sample size should be carried out, taking into account long-term academic performance metrics and teacher turnover across curriculum.

During the research, an overview of international literature on teacher stability and mobility was conducted, drawing from studies in Japan, South Korea, Saudi Arabia, and Chile. Additionally, a survey was carried out among 49 11th-grade students at our school to assess the impact of teacher turnover on quality of education. The 11th grade was selected because of its proximity to international exams, which allowed for a comparative analysis of student performance before and after teacher rotations. Many countries implement teacher rotation at the school and university levels. Staff rotation involves periodically transferring teachers to different schools or positions within a set timeframe. The primary objectives are to prevent corruption, promote experience exchange, and ensure balanced development within the education sector. For example, Japan mandates a teacher rotation policy called jinji ido, where teachers and administrative staff rotate within districts to minimize disparities between schools, maintain educational quality, and prevent teacher shortages [2]. Similarly, in South Korea, teachers must switch schools every 5-6 years as part of their career progression. Both countries have implemented rotation policies since the 1970s-80s. At King Khalid University in Saudi Arabia, a co-teaching model has been adopted, with teachers rotating between groups to collaborate on lesson planning and share expertise [3]. This model ensures smooth transitions, as the rotating teachers are highly experienced and well-prepared. In contrast, some countries prioritize teacher stability, known as looping, where the same teacher remains with a student cohort as they progress through grades. Studies suggest that teacher stability fosters stronger teacher-student relationships, as instructors become more familiar with students' strengths and weaknesses. A study conducted in Chile found that when subject teachers turnover frequently, the positive impact on students' subject knowledge is limited. In contrast, teacher stability enhances student engagement, classroom behavior, and overall learning outcomes. However, looping presents challenges, such as difficulty covering multi-year curricula and the risk of underperformance if a teacher is ineffective, potentially prolonging a student's exposure to low-quality education [4]. In the practical phase of our research, geography teachers for the 8th and 10th grades were rotated. In the 8th grade, two different teachers taught within two academic years, while in the 10th grade, the same teacher remained for three years before being replaced in the fourth year. In both grades, the new teachers collaborated to ensure consistency in lesson planning and educational quality.

At the end of primary school, students take exams in mandatory and elective subjects. The survey results showed that teachers for history of Kazakhstan was more stable. Teacher instability was observed in the elective subjects, with the highest instability in mathematics. According to the students, the change of subject teacher had little effect or often had a positive impact. However, the majority of students reported that the change of the mathematics teacher "had a negative impact." Exam results showed that the percentage of students who received a "D" in mathematics was the highest at 16.7%, while the percentage of students who received an "A*" was the lowest at 4.2%. The percentage of students who received A (20.8%) and D (16.7%) in history of Kazakhstan and mathematics was equal. The percentage of students who received A* (41.7%) and A (12.5%) was higher in elective subjects. Regarding the replaced teachers in the 8th and 10th grades, in the first quarter of the academic year, the quality of education in the selected classes was lower compared to the same period the previous year, but it gradually improved in the following quarters. This situation can be explained by the adaptation stage of students to the new teacher. As a result of the study, we came to the conclusion that: - The teacher's age and gender do not affect the quality of education. - Teacher turnover does not always negatively impact educational outcomes. Teaching experience is more influential, as experienced teachers assess students more effectively – Hattie’s highest-impact factor. - The negative impact of turnover depends on its frequency. If a teacher changes more than twice a year, student performance declines. Stability allows for better assessment and adaptation. - Collaborative lesson planning significantly enhances educational quality, as teachers exchange experiences and strategize together.

1.Hattie J. Visible learning https://www.visiblelearningmetax.com/influences 2.Seebruck, R. (2021). Independent Scholar: How Teacher Rotation in Japanese High Schools Affects the Clustering of Teacher Quality: Comparing the Distribution of Teachers across Public and Private Education Sectors. Еducation policy analysis archives, 29 (91), 1-18. https://epaa.asu.edu/index.php/epaa/article/view/5362/2663 3.Elsadig, A. (2022). Implementing Rotating Teachers Process and Co-teaching in English Class: An approach to Sustaining Saudi Students Proficiency. International Journal of Linguistics, Literature and Translation, 179-186. 4.Facundo, A., Contreras, D., & Upward, R. (2023). Let's stay together: The effects of repeat student-teacher matches on academic achievement. Economics of Education Review, 94.