This paper uses representative student data from St. Petersburg, Russia to analyze school segregation by parental socioeconomic status and student academic performance. The proposed systematic segregation indices account for ordinal variables and take expected segregation into account. We decompose segregation by school type, school, and classes and compare the results to results obtained from PISA for urban areas in Russia and six European countries. Segregation by socioeconomic status is moderate in St. Petersburg and Russia, as compared to other European countries. Segregation between schools and school types reflects parental choice, whereas within-school segregation along the lines of student performance reflects school policies.