Since the enactment of the "Education for All Handicapped Children Act of 1975" ("EHA"), Public Law (P.L.) 94-142 and its successor statute, the "Individuals with Disabilities Education Act" ("IDEA"), the secretary of the U.S. Department of Education (secretary) (and her predecessor, the commissioner of education at the U.S. Department of Health, Education, and Welfare) have been required to transmit to Congress an annual report to inform Congress and the public of the progress being made in implementing the act. The annual reports to Congress reflect a history of persistent commitment and effort to expand educational opportunities for children with disabilities. The most recent reauthorization of "IDEA" (P.L. 108-446) occurred in December 2004, and section 664(d) of the "IDEA" continues to require the annual report. With the reauthorization of "IDEA," the nation reaffirmed its commitment to improving the early intervention and educational results and functional outcomes for infants, toddlers, children, and youths with disabilities (collectively, this group may be referred to in this report as children with disabilities). The "39th Annual Report to Congress on the Implementation of the Individuals with Disabilities Education Act, 2017" describes our nation's progress in: (1) providing a free appropriate public education (FAPE) for children with disabilities under "IDEA", Part B, and early intervention services to infants and toddlers with disabilities and their families under "IDEA", Part C; (2) ensuring that the rights of these children with disabilities and their parents are protected; (3) assisting states and localities in providing for the education of all children with disabilities; and (4) assessing the effectiveness of efforts to educate children with disabilities. The report focuses on the children and students with disabilities being served under "IDEA", Part C or B, nationally and at the state level. In particular, Part C of "IDEA" provides funds to states to assist them in developing and implementing statewide, comprehensive, coordinated, multidisciplinary interagency systems to make early intervention services available to all eligible children from birth through age 2 with disabilities and their families, whereas Part B of "IDEA" provides funds to states to assist them in making "FAPE" available to eligible children ages 3 through 21 with disabilities who are in need of special education and related services. Throughout this report, individuals with disabilities who receive services under "IDEA", Part C or Part B, are referred to as infants and toddlers served under "IDEA", Part C; children served under "IDEA", Part B; or students served under "IDEA", Part B. "Special education services" is a term used throughout this report to represent services provided under "IDEA", Part B. Similarly, "early intervention services" is a term used synonymously with services provided under "IDEA", Part C. This "39th Annual Report to Congress, 2017" follows the "38th Annual Report to Congress, 2016" in sequence and format, and it continues to focus on "IDEA" results and accountability. Similar to the 38th "Annual Report to Congress, 2016", the "39th Annual Report to Congress, 2017" contains six major sections that address the five annual report requirements contained in section 664(d) of "IDEA." The sections are: (1) a summary and analysis of "IDEA" section 618 data at the national level; (2) a summary and analysis of "IDEA" section 618 data at the state level;‡ (3) a summary and analysis of the U.S. Department of Education's (Department's) findings and determinations regarding the extent to which states are meeting the requirements of "IDEA", Parts B and C; (4) a summary of special education research conducted under Part E of the "Education Sciences Reform Act of 2002"; (5) a summary of national special education studies and evaluations conducted under sections 664(a) and (c) of "IDEA"; and (6) a summary of the extent and progress of the assessment of national activities, which focus on determining the effectiveness of "IDEA" and improving its implementation. The content of this report differs from that of the "38th Annual Report to Congress, 2016" in the following ways: (1) the most recent data presented in this report represent the following applicable reporting periods: fall 2015, school year 2014-15, or a 12-month reporting period during 2014-15; (2) where data are presented for a 10-year period, the oldest data are associated with fall 2006; and (3) the "39th Annual Report to Congress, 2017" is the first annual report to present data newly collected from states: the cumulative number of infants and toddlers with disabilities who participated in Part C during the school year in addition to the longstanding point-in-time data collection (i.e., the number of infants and toddlers served under Part C on the state-designated data collection date). A summary of each of the six sections and three appendices that make up the 39th Annual Report to Congress, 2017 are contained in this document. [For the "38th Annual Report to Congress on the Implementation of the 'Individuals with Disabilities Education Act,' 2016," see ED572027.]