Congress enacted IDEA in 1970 to ensure that all children with disabilities are provided  a free appropriate public education [FAPE] which emphasizes special education and related services designed to meet their unique needs and to assure that the rights of such children and their parents or guardians are protected.

 A reading of the Act that left parents without an adequate remedy when a school district unreasonably failed to identify a child with disabilities would not comport with Congress’ acknowledgment of the paramount importance of properly identifying each child eligible for services.

 It would be particularly strange for the Act to provide a remedy, as all agree it does, when a school district offers a child inadequate special-education services but to leave parents without relief in the more egregious situation in which the school district unreasonably denies a child access to such services altogether.

 That IDEA affords parents substantial procedural safeguards, including the right to challenge a school district’s eligibility determination and obtain prospective relief is no answer. The review process is ponderous and therefore inadequate to ensure that a school’s failure to provide a FAPE is remedied with the speed necessary to avoid detriment to the child’s education.

 [T]his case vividly demonstrates the problem of delay, as respondent’s parents first sought a due process hearing in April 2003, and the District Court issued its decision in May 2005—almost a year after respondent graduated from high school.

 States expressly agree to provide a FAPE to all children with disabilities. An order awarding reimbursement of private-education costs when a school district fails to provide a FAPE merely requires the district “to belatedly pay expenses that it should have paid all along.”

 Parents are entitled to reimbursement only if a federal court concludes both that the public placement violated IDEA and the private school placement was proper under the Act.  And even then courts retain discretion to reduce the amount of a reimbursement award if the equities so warrant—for instance, if the parents failed to give the school district adequate notice of their intent to enroll the child in private school. In considering the equities, courts should generally presume that public-school officials are properly performing their obligations.  As a result … parents who “unilaterally change their child’s placement during the pendency of review proceedings, without the consent of state or local school officials, do so at their own financial risk.

 [W]e conclude that IDEA authorizes reimbursement for the cost of private special education services when a school district fails to provide a FAPE and the private-school placement is appropriate, regardless of whether the child previously received special education or related services through the public school.

 When a court or hearing officer concludes that a school district failed to provide a FAPE and the private placement was suitable, it must consider all relevant factors, including the notice provided by the parents and the school district’s opportunities for evaluating the child, in determining whether reimbursement for some or all of the cost of the child’s private education is warranted.