Girls in foster care may face difficulties across the transition to middle school. Latent growth curve modeling was employed to examine trajectories and predictors of academic competence and aggression from and against peers for 75 girls in foster care from the end of elementary school to the 2(nd) year of middle school. Across the transition to middle school, academic competence increased. Poor self-regulation was associated with decreased academic competence, and higher caregiver support was associated with increased academic competence. Frequency of aggression from peers decreased across the transition, with perceived school competence predicting smaller decreases. Aggression against peers dropped initially and then increased to pretransition levels by the end of the 2(nd) year of middle school. Lower caregiver support was associated with higher rates of aggression against peers at the end of the 1(st) year of middle school. The results are discussed in terms of implications for interventions for girls in foster care.