This three-year study aimed to investigate students' experiences with alternative seating practices (ASP) in a public-school string orchestra program. Whereas education scholarship has long demonstrated that democratic classroom seating arrangements play a crucial role in the learning process, typical orchestra classrooms maintain a hierarchical seating format assigned to students on a competitive basis. In this study I set out to explore the relationship between anti-hierarchical seating practices rooted in social justice and the musical capacity of a classroom ensemble. Using interdisciplinary methods -- ethnography, interviews, archival data collection and analysis --, I investigated ASP's effects on the learning, motivation, and musical caliber of twenty-five string orchestra students from 8th to 10th grade in a diverse public school in the United States. My research findings show that anti-hierarchical ASP fostered students' collaboration and increased their motivation and engagement. Moreover, ASP also improved drastically the musical capacity of all students, especially those with no prior music training, and it led the ensemble to win first place at statewide competitions against more affluent and advanced student orchestras for three years in a row. My study therefore suggests that pedagogy rooted in social justice can be instrumental to achieving excellence in music classrooms.