Because of the many special characteristics of charter schools, policy makers who aim to promote a system of charters schools that ensures fair access to, and fair treatment of, disadvantaged students will need a public accountability system oriented, at least in part, to equity concerns. Massachusetts, with its single statewide authorizer, as well as its system of periodic site visits to schools and specific performance criteria, illustrates such a system. In this paper, we first explain why an equity-oriented approach is important. We then describe and evaluate the Massachusetts approach, with particular attention to the information provided by the periodic site visits. Although Massachusetts does not fully succeed with all its charter schools, especially with respect to fair treatment, it is hard to make the case that charter schools will be beneficial for disadvantaged students in the absence of an accountability system of this type.