This project examines how school factors such as ethnic composition and school ideology affect group boundaries between Arab and Jewish students in Israel, focusing on three dimensions of boundaries: social relationships and mutual attitudes, lifestyles, and collective identities. The project will collect longitudinal network data in Israel schools. Based on these data, we will address three research questions. First, how and why do group boundaries vary in schools with different ethnic composition and ideologies? Second, how do group boundaries change, captured by both age and duration in school? Finally, how do different dimensions of group boundaries such as identities, lifestyles, attitudes, and friendships affect one another?