Sofia Dokuka - Candidate of Sciences in Sociology, Junior Research Fellow, Center for Institutional Studies, International Research Laboratory for Institutional Analysis of Economic Reforms, National Research University—Higher School of Economics. E-mail: sdokuka@hse.ru

Diliara Valeeva - Junior Research Fellow, Center for Institutional Studies, International Research Laboratory for Institutional Analysis of Economic Reforms, National Research University—Higher School of Economics. E-mail: dvaleeva@hse.ru

Maria Yudkevich - Candidate of Sciences in Economic Theory, Vice Rector; Director, Center for Institutional Studies, National Research University—Higher School of Economics. E-mail: yudkevich@hse.ru

Address: 20 Myasnitskaya str., 101000, Moscow, Russian Federation

Peer-effects describe the influence of social environment on individual academic achievements. Social environment is usually considered as a randomly formed group. However, it forms and develops as a result of an individual conscious dynamic choice. Students may initially choose friends among peers with similar level of academic performance, and the influence of close friends on each other’s achievements may reveal itself over time. Using stochastic actor-based models, we demarcated the boundaries between social selection and social influence evaluated through academic performance. Having analyzed the dynamics of friendship ties and academic achievements throughout the first year at university, we discovered that students were not guided by the level of academic performance when choosing friends among peers but academic achievements of the latter affected their own performance over time. This could be explained by social segregation of students based on their academic outcomes.