Many school improvement initiatives die out, are implemented superficially, or fail to improve student learning. Drawing from the literature on sustainability and organizational routines, this comparative case study examines the role organizational routines played in fostering stability and improvement in three well-established community schools. Data collection was conducted over three years and included time studies, interviews, and document review. The findings indicated that four organizational routines--leadership meetings, partnership alignment plans, quarterly data reports, and professional development--constituted a system that fostered shared responsibility, organizational capacity, commitment of resources, and collective action. The results highlight the importance of developing systems and structures that routinize beneficial norms, while also acknowledging the limits of organizational routines in prescribing individual behavior.