This paper describes and analyzes the Donors' Education Collaborative's (DEC) initiative to create sustainable systemic reform of New York City public education through projects that combined policy change strategies with efforts to develop permanent, broad-based constituencies advocating for and monitoring such reform. Based largely on field data, it examines how three DEC projects -- to create a citizens' mandate for school finance reform, develop a citywide association of grassroots organizations working to bring parent voices into education debates, and improve education for immigrant and English language learner students -- defined their goals and implemented their change strategies. The paper develops a comparative framework, based on the varied aims of the projects, and discusses projects' use of data, development of systemic approaches to systemic change, creation of links between local and systemic reform agendas, and the roles of broad, legitimated constituencies in reform efforts. It also examines how each project's goals and assumptions about how to create change were pivotal in defining and shaping a range of approaches to constituency building.