Accountability for students with disabilities who receive special education services is now a result of policy requirements in the Individuals with Disabilities Education Improvement Act (IDEA) of 2004 and the No Child Left Behind Act (NCLB) of 2001. Together these pieces of federal legislation require that students participate in statewide assessments, that their participation and results be publicly reported, and that the results of the disability subgroup factor into measures of Adequate Yearly Progress (AYP). While the basic tenets of the laws have been adjusted to add some flexibility, such as the provision that an alternate assessment based on alternate achievement standards used to measure students with the most significant cognitive disabilities, can be used to count up to 1.0 percent of the total population of students as proficient, in general the subgroup of students with disabilities is now treated similarly to other student groups in school accountability. The purpose of this Topical Review is to provide a picture of what the implementation of IDEA and NCLB has produced in terms of participation and performance in statewide accountability measures. This is accomplished by focusing on EPRRI's four case study states (California, Maryland, New York, and Texas), and partner districts within each state. It is not possible to understand the state assessment participation and performance results without having a sense of the context of the states and the districts--the student population, the history and nature of the assessment and accountability systems, and the policies that surround the assessment system, such as those related to the use of accommodations. These are investigated within this Topical Review, along with the participation and performance results of the states and districts. The diversity in results is striking, and reflective of the different policy directions that the states have taken and the different implementation avenues that the districts have pursued. In addition to variable findings is clear evidence that considerable change happens over time in states to complicate the implementation of educational reform initiatives such as those of standards-based reform and accountability for all students. The data from the four case study states reveal some unintended outcomes of reform--such as the finding that as participation increased, performance decreased. Clearly the intent of the reform was to increase participation first, and then to increase performance as well. (Contains 26 tables, 3 figures and 1 footnote.)