In the past decade much more has become known about the impacts of school vouchers on low-income families and their children. Ten years ago, the information available came primarily from an experimental public-school choice program attempted in Alum Rock, California during the 1960s But beginning in 1990 data were collected on voucher programs in many cities, including Milwaukee, Cleveland, Indianapolis, San Antonio, New York City, Washington, and Dayton, Ohio. Initially, many of these studies were limited by the quality of the data or the research procedures employed. Often, planning for the evaluation was begun after the experiment was already underway, making it impossible to gather baseline data or ensure the formation of an appropriate control group. As a result, the quality of the data collected was not as high as researchers would normally prefer.