Yuliya D. Kersha, Postgraduate Student, Junior Research Fellow, Pinsky Centre of General and Extracurricular Education; Lecturer, Department of Educational Programs, Institute of Education, National Research University Higher School of Economics. 
Address: 20 Myasnitskaya Str., 101000 Moscow, Russian Federation. E-mail: ykersha@hse.ru 

The problem of socioeconomic inequalities in Russian education takes on particular significance in the context of massification and increasingly differential quality of higher education. Relevant research is mostly focused on individual student characteristics and regional aspects. Less often, researchers’ attention is attracted to school factors, such as school socioeconomic composition (SEC) — one of the most powerful school predictors of student achievement. The effect of school composition on students’ educational trajectories remains underinvestigated, although higher education is more important for life chances than school achievement. 
In the present study, Russian data (the Higher School of Economics’ project Trajectories in Education and Careers) is used for the first time to measure the effect of school SEC on educational choices and chances of getting into college. This effect is analyzed successively for key decisions and outcomes at every stage of long-term educational trajectories. Analysis is performed with due regard to the specifics of Russian education and the sorting of students into the academic and hybrid tracks in pursuit for college degrees. 
School composition is found to be positively associated with proceeding from middle to high school, obtaining a college degree, and pursuing a Master’s degree. The largest influence of school SEC on college enrollment is observed for students who enroll in vocational studies after middle school. The compositional effect is extremely robust and persists even when student achievement and family characteristics are controlled for. Adding school SEC to the model offsets the effect of individual socioeconomic status on the likelihood of going to college, which means that exclusion of SEC from analysis may lead to invalid inferences in educational research. The effects detected cannot be explained by differences in achievement, so it would be reasonable to explore the social mechanisms behind the compositional effect in further research. School desegregation measures suggested on the basis of prior findings may turn out to be hasty and overly drastic in practice.