For the 12 years that Michael Bloomberg was mayor of New York City, the Big Apple was home to the nation's largest experiment in implementing the business model of education reform. The numbers of public school closings and new charter schools soared, while the high school student assignment system was overhauled to be driven by choice. By the…

Charter schools--what was their original promise? They would enroll diverse groups of students. They would give teachers the room and power to innovate. They would be educational laboratories that would find new ways to reach students, and they would share those lessons with other public schools. But charter schools haven't lived up to their…