The federal law No Child Left Behind (NCLB) requires states to "restructure" any school that fails for six years running to make Adequate Yearly Progress (AYP) toward full proficiency on the part of all students by the year 2014. The law provides a number of restructuring options, including turning over the school's management to a private for-profit or nonprofit entity. Only a few school districts nationwide have sought help from either type of organization in the management of low-performing schools. But in 2002 the School District of Philadelphia, at the request of the state of Pennsylvania, asked entities of both types to participate in a substantial restructuring of many of its lowest-performing schools. The restructuring initiative was directed by the Philadelphia School Reform Commission (SRC), which contracted with for-profit organizations to manage 30 elementary and middle schools and with nonprofit organizations to manage 16 schools. The policy intervention in Philadelphia raises questions of general interest: Do students at schools assigned to for-profit or nonprofit managers learn more than would be expected had those schools remained under school district management? Is for-profit management more or less effective at raising achievement than nonprofit management? Told most simply, the Philadelphia story provides a threefold answer to these questions: (1) for-profits outperform district-managed schools in math but not in reading; (2) nonprofits probably fall short of district schools in both reading and math instruction; and (3) for-profits outperform nonprofits in both subjects. However, the answers require both explication and qualification. In this article, the authors use a rigorous research design to estimate the impact of for-profit and nonprofit management in Philadelphia. (Contains 1 figure.)