This is the "43rd Annual Report to Congress on the Implementation of the Individuals with Disabilities Education Act, 2021." Section 664(d) of the Individuals with Disabilities Education Act (IDEA), as reauthorized in 2004, requires that the Department of Education report annually on the progress made toward the provision of a free appropriate public education to all children with disabilities and the provision of early intervention services to infants and toddlers with disabilities. The "43rd Annual Report to Congress on the Implementation of the Individuals with Disabilities Education Act, 2021" 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 IDEA services to all children with disabilities; and (4) assessing the effectiveness of efforts to provide IDEA services to children with disabilities. The report focuses on children with disabilities being served under IDEA, Part B and Part C, nationally and at the State level. [For the "42nd Annual Report to Congress on the Implementation of the Individuals with Disabilities Education Act, 2020," see ED612645.]