School bullying is increasingly viewed by researchers as a group phenomenon that extends beyond the perpetrator-victim dyad and is embedded in the wider social context. This paper reviews the literature on classroom and school factors contributing to bullying and victimization among children and adolescents. Considerable variability in the prevalence of these problems exists between classrooms and schools, which are highly relevant contexts for students' social development. Along with individual characteristics, both classroom- and school-related factors explain the bullying dynamic. The contexts may also exacerbate, or buffer against, the effects of individual-level risk for bullying involvement and the consequences of victimization. We discuss findings on the contributions of demographic and structural characteristics (e.g. grade level, classroom and school size), peer contextual factors (e.g. status hierarchy, group norms and bystander behaviours) and the role of teachers. Finally, implications for research and school-based antibullying programs are considered. Copyright (c) 2014 John Wiley & Sons, Ltd.