This study evaluated a school-based intervention to enhance adolescent peer relationships and improve functional outcomes, building upon Ed Zigler’s seminal contribution in recognizing the potential of academic contexts to enhance social and emotional development. Adolescents (N = 610) primarily from economically or racially/ethnically marginalized groups were assessed preintervention, postintervention, and at 4-month follow-up in a randomized controlled trial. At program completion, intervention participants reported significantly increased quality of peer relationships; by 4-month follow-up, this increased quality was also observable by peers outside of the program, and program participants also displayed higher levels of academic engagement and lower levels of depressive symptoms. These latter effects appear to have potentially been mediated via participants’ increased use of social support. The potential of the Connection Project intervention specifically, and of broader efforts to activate adolescent peer relationships as potent sources of social support and growth more generally within the secondary school context, is discussed.