In 1995, the. Illinois state legislature declared that an "educational crisis" existed in Chicago and passed the Chicago School Reform Amendatory Act, which integrated school governance by placing authority for the public schools under the control of the mayor reducing the number of policy actors who compete for decision-making authority and expanding the financial and management powers of the district administration. Although the new district administration effectively used the integrated governance structure to improve operations management and to strengthen the system's political base, reconstructing teaching to improve student achievement presents a much more difficult challenge. In this article, the authors examine how the district's probation policy affected curricular and instructional practices in two low-performing Chicago high schools. Their review of policy implementation processes reveals how "street-level bureaucrats" strongly mediated the effects on classroom teaching.