This research examined developmental trajectories for social and physical aggression for a sample followed from age 9 to 18, and investigated possible family predictors of following different trajectory groups. Participants were 158 girls and 138 boys, their teachers, and their parents (21% African American, 5.3% Asian, 51.6% Caucasian, and 21% Hispanic). Teachers rated children's social and physical aggression yearly in grades 3–12. Participants' parent (83% mothers) reported on family income, conflict strategies, and maternal authoritarian and permissive parenting styles. The results suggested that both social and physical aggression decline slightly from middle childhood through late adolescence. Using a dual trajectory model, group‐based mixture modeling revealed three trajectory groups for both social and physical aggression: low‐, medium‐, and high‐desisting for social aggression, and stably‐low, stably‐medium, and high‐desisting for physical aggression. Membership in higher trajectory groups was predicted by being from a single‐parent family, and having a parent high on permissiveness. Being male was related to both elevated physical aggression trajectories and the medium‐desisting social aggression trajectory. Negative interparental conflict strategies did not predict social or physical aggression trajectories when permissive parenting was included in the model. Permissive parenting in middle childhood predicted following higher social aggression trajectories across many years, which suggests that parents setting fewer limits on children's behaviors may have lasting consequences for their peer relations. Future research should examine transactional relations between parenting styles and practices and aggression to understand the mechanisms that may contribute to changes in involvement in social and physical aggression across childhood and adolescence. Aggr. Behav. 9999:XX–XX, 2014. © 2014 Wiley Periodicals, Inc.