DescriptionThis dissertation examines the organizational and group-level cultural processes that shape the context for peer interpersonal aggression in high schools. I use a mixed- methods approach to understand how behavioral norms in schools are formed at the organizational level of the school, and are communicated, enacted, and reshaped in small groups. The extent to which these norms vary in small groups, or classrooms, impacts the conditions for learning within them. Currently the majority of school victimization research focuses patterns of behavior at the school-wide level, without accounting for variation in micro-level contexts within the school. I situate the classroom as a key site of interactions between students. I use the School Climate Understanding and Building Aspirations (SCUBA) Survey to capture patterns of victimization and students’ perceptions and attitudes related to personal aspirations and school-wide norms. I conducted ethnographic observations in two high schools across a full academic year to observe grounded interactions over time. I also conducted in-depth interviews with students sampled from the observed classrooms. I argue that three main cultural factors shape the context for aggression in schools and classrooms. These are 1) academic and aspirational norms; 2) disciplinary norms and practices; and 3) the everyday practices that develop in classrooms. Variation in observed aggressive behavior between schools is primarily shaped by these cultural factors. Within school variation is primarily shaped by how these cultural elements are enacted within local classroom idiocultures, which are differentiated according to the classroom’s academic tracking level, the teacher, and the peer group. This study provides a grounded understanding of the cultural roots of aggressive behavior, and expands our understanding of how victimization varies across and within schools. Future efforts to reduce student interpersonal aggression and improve learning conditions should include measurement protocols and interventions focused on the key cultural factors identified, which take place at both the school-wide and classroom levels.