Much of the research on individual attainment in educational settings has focused on individual differences. This chapter sets out the role of groups and group processes. After reviewing evidence for the role of social comparison in the classroom, and theory and research on ethnic group differences, we consider the impact of category memberships, stereotypes, and threat on educational performance. We introduce social identity theory and explain its relevance to educational outcomes. We then offer an integrative social identity model for education (SIME) that incorporates three elements of education research: social comparison, stereotypes, and identity. The model provides a more comprehensive perspective on the role of intergroup and intragroup relations and indicates how (and which) group memberships can present barriers to, or reveal new horizons for, performance and achievement. We describe how these elements may work together in practice and conclude by considering prospects and approaches for future research.