There is a paucity of research on the causal relationship between arts learning and educational outcomes. Investigating these relationships has become imperative as policymakers increasingly prioritize empirical evidence of educational impacts, which often leads to curriculum narrowing that favors traditionally-tested subjects. Employing a randomized controlled trial with 42 elementary and middle schools in Houston, Texas, we find that randomly assigning arts educational opportunities reduces disciplinary infractions, improves writing achievement, and increases students' emotional empathy. Students in elementary schools, which were the primary focus of the program, also experience increases in school engagement, college aspirations, and cognitive empathy. As the first large-scale randomized control trial of arts learning in an authentic school setting, these findings provide strong evidence that the arts can produce meaningful impacts on students' academic outcomes and social-emotional development. Education policymakers should consider these benefits when assessing the role of the arts in schools.