This article presents a field-tested approach for integrating music arranging into middle and high school music ensembles. This project-based unit of study builds on scholarship in informal music learning and social constructivism. Reflections from former high school students who participated in the project help illuminate these connections. The article provides planning and assessment documents, recognizes students' successes, proposes solutions to challenges encountered, and reports outcomes. The article and supplemental documents demonstrate how student-led, small-group music arranging can infuse middle and high school ensembles with student creativity and choice while providing opportunities for group collaboration.