Over the past decade, the standards-based reform movement in education has focused attention on the responsibility of schools and school systems to produce results in student learning. Nationally this focus is most evident with the implementation of accountability provisions of the federal No Child Left Behind (NCLB) Act of 2001. However, even prior to NCLB, many states and districts had instituted their own performance-based accountability programs. In 1999, the California legislature approved the Public Schools Accountability Act (PSAA), which incorporated three central components designed to hold schools accountable for improving student outcomes. In June 2003, AIR completed the first legislatively mandated study of the PSAA, with support from Policy Analysis for California Education (PACE) and EdSource. In November 2004, AIR was contracted by the California Department of Education to conduct a continuation study of the II/USP component of PSAA. Building on the findings from the 2003 PSAA evaluation, this study was designed to provide follow-up information on the overall impact of the II/USP program and on the factors and strategies that have contributed to growth in selected low-performing schools. In addition, since II/USP has evolved to incorporate the School Assistance and Intervention Team (SAIT) process, AIR examined this component of the policy specifically. This report provides the details of the study and an in-depth discussion of AIR's findings in four main areas: (1) the overall impact of II/USP on student achievement; (2) factors contributing to or hindering growth within II/USP schools; (3) the role of the district in school improvement efforts; and (4) the impact of NCLB implementation on the focus and implementation of the state accountability program. Appended are: (1) Supplementary Methods and Tables for the Achievement Analysis; (2) Supplementary Exhibits; and (3) Interview Protocols. (Contains 36 exhibits.)