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 time Bloomberg left office, relations between the school district administration and the district's teachers had fallen to a record low--but the hoped-for improvements in student achievement had not materialized. In this article, Greg Anrig compares the adversarial approach to school improvement typified by New York City under Bloomberg--which pits teachers and their unions against "reformist" district administrations--with a collaborative approach that a number of districts have adopted. He describes how administrators in urban districts like Cincinnati, Ohio; Springfield, Massachusetts; and Hillsborough County, Florida, have reached out to teachers and teacher unions to develop collaborative school improvement efforts that have produced impressive results.