Social and emotional skills are the ability that individuals possess in the process of achieving goals, cooperating with others and managing emotions1. It is expressed in the individual's persistent and stable thinking, feelings and behavioral stereotypes. The importance of social and emotional skills has attracted increasing attention in education around the world since the release of the global test results of the Social and Emotional Skills Assessment by the OECD in 2021. Studies have shown that social and emotional skills are essential conditions for students' success, an important predictor of career achievement, and closely related to individual physical and mental health and long-term happiness2-4. Under the long-term influence of the traditional college entrance examination system and the concept of exam-oriented education, Chinese education has over-emphasized the cultivation of students' cognitive abilities and relatively neglected the important value of social and emotional skills. In this context, the cultivation of students' social and emotional skills is not only a practical exploration that is urgently needed in today's China in order to improve the quality of education
and promote the all-round development of human beings, but also an educational transformation advocated in response to the rapid changes in the global socio-political environment and the creation of a new social contract.
Teachers are the first determinant of the quality of education and have a direct impact on the development of students' social and emotional skills5,6. Under the social system of free flow of labor factors.as rational economic beings, teachers will make employment choice decisions after comprehensively considering multiple factors such as career development, family, school, and social environment. Generally speaking, teachers with strong capital and outstanding ability are more likely to choose to flow from weak schools in backward areas to high-quality schools in developed areas7-10, resulting in more unbalanced allocation of teachers in regional, urban and rural schools, and inter-school schools, thus aggravating the disparity in the development status of students and educational inequality. In order to optimize the allocation of teacher resources so that every student can enjoy a fair and quality education as far as possible, countries around the world have explored two distinct development paths. The first path, represented by Europe and the United States, focuses on exploring effective measures to reduce teacher mobility from a market perspective, giving full play to the role of the market mechanism in the allocation of teacher resources, and allowing high-quality teachers to stay in underprivileged schools to teach11. The first path is represented by countries in Europe and the United States. The second path, represented by countries such as China, Japan and South Korea, focuses on government mobility policies that enforce regular teacher mobility and direct quality teachers to work in underprivileged schools as much as possible from a government deployment perspective12-14. The main objective is to guide high-quality teachers to work in underprivileged schools as much as possible.
So how does teacher mobility affect student development? Why has the Chinese government chosen a very different path from that of Europe and the United States? Is there really value in using policy instruments to promote regular teacher mobility? Teacher mobility refers to the flow of teachers from one school to work in another. Analysis from a systemic perspective reveals that teacher mobility involves two organizations and their members (leaders, colleagues, students, etc.) in both flowing and inflowing schools, and that mobile teachers leave familiar social network relationships in flowing schools and enter unfamiliar ones in inflowing schools, which does not have the same impact on the development of students in the two types of schools. In terms of existing research, European and American scholars focus on the influencing factors of teacher mobility and its impact on students in flowing schools, with a view to using empirical evidence to prove the negative impact of teacher mobility on the development of students in flowing schools, and thus calling for the stabilization of the teaching force. However, Chinese scholars, under the theoretical expectation that teacher mobility can promote the development of students in underprivileged schools, explore the dilemmas of teacher mobility policy implementation and its causes, with a view to optimizing teacher mobility policy to promote more teacher mobility to underprivileged schools, and to genuinely improve the development of students in underprivileged schools by optimizing teacher mobility policy, so that regular teacher mobility can be realized in practice.
In China, since the reform and opening up of China in 1978, under the influence of multiple factors such as the urban-rural dichotomy, the development strategy of "the first to get rich will drive the poverty to get rich", and the policy of focusing on school education, a large number of excellent teachers have been concentrated in county and city schools through independent mobility and government deployment, and the difference between the teacher strength of urban and rural schools has been widening. As a result, in 1995, the Chinese government issued the Opinions on Strengthening the Construction of Primary and Secondary School Teachers during the Ninth Five-Year Plan Period, which proposed for the first time that "regular exchanges of teachers should be actively carried out ...... and effective mechanisms for the mobility of teachers should be established, and effective measures should be taken to ensure that teachers can be transferred to other schools. An effective mechanism for teacher mobility should be established, and practical policy measures should be taken to encourage teachers to move from urban to rural areas and from privileged to underprivileged schools15."
After nearly 30 years of exploration, China's teacher mobility policy has gone through three phases: policy inception, rotational exchanges, and county-managed and school employment16.At the stage of county-managed and school employment, the Chinese government raises the unit of attribution of the teacher's establishment from the school to the county education administration department. This transition will transform teachers from being "unit persons" within schools to becoming "system persons" within counties, effectively addressing personnel separation issues during rotational exchanges stage17,and truly promote the regular mobility of teachers. However, field investigations have found that negative perceptions of policies such as 'a farce' and 'Matthew effect' have emerged in an endless stream, principals' disapproval, teachers' inactivity, parents' distrust, and students' inadaptation have also led to the implementation of policies in some areas being hampered18-21. The reason for this is that stakeholders are still skeptical about the scientific and standardized nature of the county-managed and school employment policy. In particular, the uncertainty of the effects of teacher mobility has hindered the acceptance of the policy and its in-depth promotion.
In view of this, this study uses SESS 2019 Suzhou data and OLS regression, quantile regression, interaction terms to explore the impact of teacher mobility on the development of students' social and emotional skills. The main contributions of this study are as follows: this study utilizes large-scale survey data and quantitative data analysis methods to examine the effects of teacher mobility on students' social and emotional skills and its heterogeneity, to provide empirical evidence in China for the study of the effects of teacher mobility, deepen the comprehensive understanding of the effects of teacher mobility on students' development, and make up for the gaps in the previous studies.
Teacher mobility and student development
Teacher mobility is a classic topic in the field of teacher research, and related terms also include teacher attrition, turnover, and rotation. Although the above concepts differ from each other, they all have a core commonality that teachers need to leave from one school. In other words, regardless of the type, the impact on student development is similar in that it involves the departure of one old teacher and the replacement of one new teacher. Simultaneously, considering the relatively small amount of literature on teacher mobility, this study expands the scope of the literature search to include relevant lexical literature for a unified sorting. It is found that the existing studies have not yet reached a consistent conclusion, which may be related to national conditions, teacher policies and the specific context of teacher mobility. Generally speaking, views on the impact of teacher mobility on student development can be broadly categorized into three types: negative, positive and neutral.
From the perspective of negative impact, teacher mobility has a direct negative effect on the development of students in teaching classes in the flowing school, and has an indirect negative effect on students in other classes. In terms of direct effect, theoretically, the same teacher teach the same class of students, teachers and students can familiarize and adapt to each other in both directions, thus forming a good teacher-student relationship quickly and efficiently22,23, teachers can also teach students in accordance with their aptitude according to the human capital status of specific students to improve the quality of teaching24. However, teacher mobility will inevitably lead to a failure of the above advantages, disrupting the coherent implementation of the school teaching program25. The fact that new teachers need time to understand the specific situation of students, familiarize themselves with the teaching program, reshape a good relationship between teachers and students. Therefore, teacher mobility will have a negative impact on student academic achievement. An analysis using the proportion of teachers on the verge of retirement as an instrumental variable found that there is a significant negative correlation between teacher mobility and student KS4 scores, with each 10 percent point increase in the proportion of retirements decreasing student KS4 scores by approximately 2.4 standard deviations26. A study based on Chilean data also found that repeat student-teacher matches contributed significantly to students' academic achievement, with effect sizes equal to 0.1-0.2 standard deviations of the value-added to students' achievement27. In terms of indirect effect, a teacher is not only a teacher in a class, but also a member of the school organization. Teacher mobility can also have a negative spillover impact on the development of students' academic achievement in other classes by undermining school teacher cooperation and trust, positive school climate25,28. The fixed panel effect estimation results of the fourth and fifth grade students in New York City indicate that the higher the teacher mobility rate, the worse the English and mathematics scores of the grade students, and there is a significant negative impact on the students in the school's teacher retention class29.
From the perspective of positive impact, teacher mobility can promote the high-quality development of students in the inflowing schools by promoting professional development, improving the quality of human-job matching and exerting the "catfish effect". Firstly, teacher mobility can enrich their teaching experience in facing different types of student groups, improve their teaching ability, promote work innovation, and increase the "energy" reserve of mobile teachers14,30. Secondly, moderate teacher mobility can improve the quality of human-job matching, so that mobile teachers can give full play to their own abilities in an appropriate environment. Labor economics research indicates that employees with higher matching quality tend to obtain higher income and productivity31, as well as in the field of education. The study found that the human-job matching effect explains about one-quarter of the teacher quality effect in the usual sense, and that this effect exists only in specific schools and does not migrate due to teacher mobility; teachers with poor human-job matching are more likely to participate in inter-school mobility and show higher productivity in their new schools32. Thirdly, organizational management research shows that employee communication can break the closed state of the system, new employees can inject new ideas and new vitality into the new organization33, exert the 'catfish effect' to stimulate the work vitality of school teachers and alleviate job burnout.
From the perspective of neutral impact, the change of compositional quality of mobile teacher and replacement teacher is a key factor of the effect of teacher mobility. Theoretically, when the quality of mobile teacher is lower than that of replacement teacher, teacher mobility will have a positive impact on students' academic development; when the quality of mobile teacher is higher than that of replacement teacher, this effect becomes negative. When the quality of the two is basically the same, then the impact of teacher mobility will also be nearly zero. In other words, the relative quality of mobile and replacement teacher determines the determinants of the effect of teacher mobility29.Hanushek and Rivkin simulated the replacement of mobile teachers by new teachers, and found that the overall impact of teacher mobility on student development was not significant34. There is a certain difference between the simulated data and the actual educational practice. Adnot 's study of American Columbia public schools through the difference-in-difference method found that after adopting the IMPACT teacher performance evaluation and incentive system, the low-efficiency teachers turnover will have a significant positive impact, while the high-efficiency teachers turnover will have a negative impact, but not significant35. Barbieri evaluated the effect of Italian teacher mobility and found that the mobility rate of teachers in the flowing school has a significant negative impact on students' academic achievement, while the mobility rate of teachers in the inflowing school has a significant positive impact on students' academic achievement36. Another study also found that the effect of repeated matches between Chilean mathematics teachers and students on mathematics achievement was almost zero. Education management personnel should not blindly pursue, do not deliberately avoid37.
In summary, the existing literature has laid a solid theoretical foundation and empirical research support for the conduct of this study, but there are still the following deficiencies. Firstly, there is a lack of empirical research based on Chinese data. In China, government departments promote teacher mobility policies and to promote more excellent teachers to work in underprivileged rural schools. There is a basic assumption behind this measure: teacher mobility can promote the improvement of the quality of education in underprivileged schools. Otherwise, there would be no need for government departments to invest a great deal of time, energy, and financial resources in promoting teacher mobility. However, as mentioned above, the relationship between teacher mobility and student development is complex, which leads to the obstruction of the implementation of teacher mobility policy to a certain extent. The actual effect of teacher mobility in China needs to be verified by empirical research. However, almost all the relevant research of Chinese scholars stops at the theoretical level, and there is no any Chinese empirical research based on large-scale survey data30,38,39. Secondly, there is a lack of attention to social and emotional skills. Social and emotional skills is an important dimension of modern students' core competitiveness. However, due to the limitations of previous data, the existing studies have only explored the effects of teacher mobility on students' academic achievement. There are no studies that analyze the role of teacher mobility on students' social and emotional skills, and the estimation of the effects of teacher mobility may be biased. Thirdly, there is a lack of attention to group heterogeneity. Previous studies have focused on exploring the average effect of teacher mobility on student development. Lack of analysis and discussion of group heterogeneity.
Objectives and hypotheses of the study
This study had two objectives. The first objective was to examine the associations between teacher mobility and student's social and emotional skills in the group of 10-year-old and 15-year-old students in Suzhou, China in the SESS survey. The second objective was to explore the potential differences in the impact of teacher mobility on the social and emotional skills of students of different gender, socioeconomic status and development level.
Therefore, this study proposed four hypotheses:
Hypothesis 1: After controlling for other variables, teacher mobility has a significant impact on students' social and emotional skills.
Hypothesis 2: The gender of students moderates the influence of teacher mobility on students' social and emotional skills.
Hypothesis 3: The family socioeconomic status of students moderates the influence of teacher mobility on students' social emotional ability.
Hypothesis 4: There are differences in the impact of teacher mobility on students' social and emotional skills at different locations.