OSEP’s Annual Report to Congress.
The Office of Special Education Programs (OSEP) within the US Department of Education, has oversight for the implementation of the Individuals with Disabilities Education Act (IDEA). OSEP prepares an annual report to Congress that includes substantial statistical data (number of children identified, etc.) on special education.
http://www2.ed.gov/about/offices/list/osers/osep/research.html
Data Accountability Center | DAC.
The DAC provides public access to the most recent State-reported data available collected by OSEP at the U.S. Department of Education, as required under Section 618 of IDEA.
https://www.ideadata.org/default.asp
NCEO | National Center on Educational Outcomes.
NCEO provides national leadership in the participation of students with disabilities in national and state assessments, standards-setting efforts, and graduation requirements. NCEO maintains an online accommodation bibliography that allows you to search a compilation of empirical research studies on the effects of various testing accommodations for students with disabilities. NCEO offers information on assessments, accountability policy and practices, national and state data collection programs, and standards-setting for all students, including those with disabilities.
http://www.cehd.umn.edu/nceo/