Behaviors that warrant school discipline (e.g., fighting, victimizing peers) is detrimental to school climate and the learning process. This study examines the effectiveness of preventing school disciplinary incidents in middle school through an experiential, social and emotional learning (SEL) program. A community youth development organization, two public middle schools in low-income communities and a local university collaborated to design and deliver the program to all seventh-grade students in social studies curricula. This article describes the design of the intervention and its effect on students' suspensions, skipping class, and failing grades. The results of this study indicate that a school-based SEL service-learning program may reduce disciplinary incidents for middle school students. Other attitudes and skills, however, did not change significantly in the anticipated direction. This research demonstrates the effect of SEL curricula and service-learning programs embedded in school coursework. Implications for practice and research include understanding mechanisms of change in SEL processes.