AbstractThe effects of conflict resolution training on students' moral reasoning were examined in this five‐year study. Inspired by pilot studies that found increased attachment, cooperation, and prosocial skills in treatment classrooms, the study was conducted with elementary students (ten treatment groups and eight comparison groups) in a low‐income Philadelphia school and in two schools in a suburban low‐income district. Treatment group teachers were trained in integrated conflict resolution strategies, and they were provided ongoing support to ensure classroom implementation of conflict resolution skills. Treatment group students demonstrated significant improvement in moral reasoning.