Many proponents of charter schools suggest that, by providing an option outside traditional public schools, they are helping disadvantaged students who might otherwise be confined to low-quality neighborhood schools. But market-based accountability structures are insufficient to ensure that charter schools are actually enrolling students (i.e., students from economically distressed families, students with disabilities, English learners, and students of color) and, once they are enrolled, providing them sufficient support. Helen Ladd and Edward Fiske use the Massachusetts system of authorization, data collection, and site visits to illustrate a high quality public accountability system for charter schools that is focused on promoting equity.