For the purpose of Institute's special education research programs, a student with a disability is defined in Public Law 108-446, the Individuals with Disabilities Education Improvement Act of 2004 (IDEA), as a child "(i) with mental retardation, hearing impairments (including deafness), speech or language impairments, visual impairments (including blindness), serious emotional disturbance (referred to in this title as ‘emotional disturbance'), orthopedic impairments, autism, traumatic brain injury, other health impairments, or specific learning disabilities; and (ii) who, by reason thereof, needs special education and related services" (Part A, Sec. 602). An infant or toddler with a disability is defined in IDEA as, "an individual under 3 years of age who needs early intervention services because the individual (i) is experiencing developmental delays, as measured by appropriate diagnostic instruments and procedures in 1 or more of the areas of cognitive development, physical development, communication development, social or emotional development, and adaptive development; or (ii) has a diagnosed physical or mental condition that has a high probability of resulting in developmental delay" (Part C, Sec. 632).

Applicants proposing to study children at risk for developing disabilities must present research-based evidence of an association between risk factors in their proposed sample and the potential identification of specific disabilities. The determination of at risk for disabilities status must be made on an individual child basis and may include, for example, factors used for moving children to higher tiers in a Response to Intervention model. The method to be used for determining if a child is at risk for developing a specific disability must be made explicit in applications and must be completed as part of the sample selection process. Evidence consisting only of general population characteristics (e.g., labeling children as "at risk for disabilities" because they are from low income families or are English learners) is not sufficient for this purpose. In addition, applicants must identify the disability or disability categories that the sampled children are at risk of developing.