Objective: Little is known about which aspects of after-school programs bolster the developmental milestones required for children to thrive intellectually, socially, and academically. To help close this gap, we examined the effects of an El Sistema-inspired (ESI) after-school music education program to identify the intervention’s social, educational, and developmental health outcomes. Method: The ESI after-school program was provided to 93 fifth-grade students in a racially and ethnically diverse, low-income elementary school in Ann Arbor, MI, over 4 years. We assessed program effects with a mixed-methods design that included preprogram and postprogram participant surveys, interviews with music instructors and the school principal, and parent and participant focus groups. Results: From pretest to posttest, we found significant changes in students’ perception of their music-making ability and in their connection to other students. Participants also noted an enhanced sense of school pride and broader community recognition. Conclusions: Findings suggest that providing after-school music education in racially and ethnically diverse low-income communities may be an effective strategy for enhancing personal agency, strengthening school connections, and fostering school pride in children. (author abstract)