Robert Busching, Barbara Krahé

• This article investigated how the development of deviant behavior in adolescence is influenced by the variability of deviant behavior in the peer group. Based on the social information-processing (SIP) model, we predicted that peer groups with a low variability of deviant behavior (providing normative information that is easy to process) should have a main effect on the development of adolescents’ deviant behavior over time, whereas peer groups in which deviant behavior is more variable (i.e., more difficult to process) should primarily impact the deviant behavior of initially nondeviant classroom members. These hypotheses were largely supported in a multilevel analysis using self-reports of deviant behavior in a sample of 16,891 adolescents in 1,308 classes assessed at two data waves about 1-year apart. The results demonstrate the advantages of studying cross-level interactions to clarify the impact of the peer environment on the development of deviant behavior in adolescence.