Formerly excluded from measures of educational performance, students with disabilities (SWDs) are now explicitly recognized in federal and state accountability systems. At the national level, the 1997 amendments to the Individuals with Disabilities Education Act (IDEA) laid the foundation for accountability of SWDs by requiring states to include these students in state and district assessments and to report their participation and performance. This requirement was further reinforced by the Elementary and Secondary Education Act (ESEA), as reauthorized in 2001, which established SWDs as an explicit student subgroup for the purpose of determining whether schools make adequate yearly progress (AYP). This interim study report presents an overview of the relevant policy context and presents findings for the following research questions: (1) What percentage of schools were accountable for the performance of the SWD subgroup between the 2005-06 and 2008-09 school years?; (2) What percentage of different types of schools were accountable for the performance of the SWD subgroup?; (3) What percentage of schools moved in and out of accountability for the performance of the SWD subgroup?; (4) What percentage of schools missed AYP because of the performance of the SWD subgroup?; and (5) What percentage of schools accountable for SWD subgroup performance were identified for school improvement? The study is based on data from ED"Facts", a U.S. Department of Education (ED) initiative to collect and place K-12 performance data at the center of policy, management, and budget decisions. The analyses that appear in this interim report are limited to the 2005-06 to 2008-09 school years because 2005-06 is the first year in which ED"Facts" collected information on the number of tested SWDs and 2008-09 was the latest year for which ED"Facts" data were available at the time the analyses were conducted. The final study report will extend the interim report analyses with an additional year (2009-10) of ED"Facts" data and also will examine school practices that may relate to the achievement outcomes of SWDs, drawing on data from a school survey administered in 2011. In addition, the final report will explore the relationships between school SWD-accountability status and school practices and SWD proficiency. Key findings for each of the research questions addressed in this report are summarized as follows: (1) "What percentage of schools were accountable for the performance of the SWD subgroup between the 2005-06 and 2008-09 school years?" (a) Across the 40 states with relevant data for the 2008-09 school year, more than a third (35 percent) of public schools were accountable for the performance of the SWD subgroup, representing 58 percent of tested SWDs in those states. In those same 40 states, 62 percent of middle schools were accountable for SWD performance, while 31 percent of elementary schools and 23 percent of high schools were accountable; (b) In the 20 states that had relevant data for all 4 years, there was a steady increase in the percentage of SWD-accountable schools, from 25 percent in the 2005-06 school year to more than a third (34 percent) in the 2008-09 school year; (2) "What percentage of different types of schools were accountable for the performance of the SWD subgroup?" (a) In the 40 states with relevant data, 12 percent of regular charters were accountable for SWD subgroup performance in the 2008-09 school year, compared with over one-third (37 percent) of traditional regular schools, 40 percent of traditional special education schools, and 40 percent of special education charters; (b) In the 40 states with relevant data, the percentage of tested SWDs represented in SWD-accountable schools in the 2008-09 school year ranged from 33 percent for vocational/alternative schools to 82 percent for special education charters; (3) "What percentage of schools moved in and out of accountability for the performance of the SWD subgroup?" (a) In the 32 states with relevant data, the majority (55 percent) of the public schools were not accountable for the SWD subgroup in any of the 4 years examined, in comparison with 18 percent of the schools that were consistently accountable in each of the 4 years; (b) There was year-to-year fluctuation in schools' accountability for the SWD subgroup among the remaining schools, which were accountable for the SWD subgroup in some years but not all 4 years. Among the schools accountable for the SWD subgroup in the 2005-06 school year in the 32 states with relevant data, 80 percent, 78 percent, and 76 percent also were accountable in the following 3 school years, respectively; (4) "What percentage of schools missed AYP because of the performance of the SWD subgroup?" (a) Nine percent of all public schools in 37 states missed AYP in the 2008-09 school year because of SWD subgroup performance and other reason(s), and 5 percent missed it solely because of SWD subgroup performance. Together these schools represented more than a quarter (28 percent) of tested SWDs in all public schools in these states; (b) Among schools accountable for SWD subgroup performance in these 37 states, 26 percent missed AYP because of SWD performance and other reason(s), and 14 percent missed AYP solely because of SWD performance in the 2008-09 school year. Combined, these schools enrolled 47 percent of tested SWDs attending SWD-accountable schools in these states; (c) In the 16 states that had relevant data over the 4 years analyzed, 40 percent of SWD-accountable schools missed AYP either partially or solely due to SWD performance in the 2005-06 school year and 35 percent did so in 2008-09; (5) "What percentage of schools accountable for SWD subgroup performance were identified for school improvement?" (a) Among schools that were consistently accountable for the performance of the SWD subgroup across 27 states during the 4 years, the majority (56 percent) were never identified for school improvement over this time period. By comparison, among schools that were consistently not accountable for SWD subgroup performance in these states, three-quarters (76 percent) were never identified for improvement; (b) Identification for school improvement was mostly stable over time. Of the consistently SWD-accountable schools in 27 states, 80 percent of the schools identified for improvement as well as schools not identified for improvement in the 2006-07 school year retained the same identification status through 2009-10. Appended are: (1) Technical Working Group Members; (2) Minimum subgroup size for AYP determination, by state, 2007-08 school year; (3) Number and percentage of public schools accountable for SWD subgroup performance and the percentage of tested SWDs in SWD-accountable schools in 40 states with relevant data, 2008-09 school year; (4) Number and percentage of public elementary schools accountable for SWD subgroup performance and the percentage of tested SWDs in SWD-accountable elementary schools in 40 states with relevant data, 2008-09 school year; (5) Number and percentage of public middle schools accountable for SWD subgroup performance and the percentage of tested SWDs in SWD-accountable middle schools in 40 states with relevant data, 2008-09 school year; (6) Number and percentage of public high schools accountable for SWD subgroup performance and the percentage of tested SWDs in SWD-accountable high schools in 40 states with relevant data, 2008-09 school year; (7) Average enrollment for schools accountable and not accountable for SWD subgroup performance, in 40 states with relevant data, 2008-09 school year; (8) Percentage of urban and rural schools, percentage of students eligible to receive free or reduced-priced lunch, and percentage of minority students, for schools accountable and not accountable for SWD subgroup performance, in 40 states with relevant data, 2008-09 school year; (9) Percentage of public schools accountable for SWD subgroup performance, in 20 states with relevant data, 2005-06 to 2008-09 school years; (10) Tested SWDs in public schools accountable for SWD subgroup performance as a percentage of tested SWDs in all public schools, in 20 states with relevant data, 2005-06 to 2008-09 school years; (11) Percentage of public schools accountable for SWD subgroup performance, in 32 states with relevant data, by the number of years in which they were accountable between the 2005-06 and 2008-09 school years; (12) Percentage of public schools consistently accountable for SWD subgroup performance in all 4 years (2005-06 to 2008-09 school years), in 27 states with relevant data, by the year identified for school improvement; and (13) Percentage of public schools consistently not accountable for SWD subgroup performance in all 4 years (2005-06 to 2008-09 school years), in 27 states with relevant data, by the year identified for school improvement. (Contains 28 exhibits and 42 footnotes.)