Ability–Achievement Discrepancy

The ability–achievement discrepancy is defined as a statistically significant difference between a child’s score on a measure of achievement in one or another academic domain such as reading or math and the child’s score on a measure of intellectual ability, typically in the form of IQ. For a considerable period of time, the IQ-achievement discrepancy was the central criterion used by educators, school psychologists, and educational researchers to define specific learning disabilities in otherwise normal children. This entry discusses the history of the ability–achievement discrepancy, the origin of [Page 11]its use, and problems with its use to identify individuals with specific reading disability.

The use of the ability–achievement discrepancy criterion has a long history that dates back to Samuel Kirk and Barbara Bateman’s suggestion that learning disabilities can be defined as a collection of developmental disorders of neurological origin that affect various types of school-based learning in children who are not mentally challenged or impaired by extraneous impediments to learning such as sensory deficits, emotional disorders, or socioeconomic disadvantage. The Education for All Handicapped Children Act (U.S. Public Law 94–142, later renamed the Individuals with Disabilities Education Act), adopted in 1975, mandated that learning disabilities be defined as the occurrence of achievement deficits in otherwise normal children who have at least average intelligence.

The Education for All Handicapped Children Act had significant impact because it led to the use of intelligence as a defining criterion in most state definitions of learning disability, typically in the form of an IQ-achievement discrepancy in one or another academic domain. The IQ-achievement discrepancy eventually became widely adopted as a basic prerequisite for diagnosing learning disabilities in schools and other institutions and for defining learning disabilities in empirical research studying the etiology and nature of hypothesized impediments to success in school learning.