In the early 1900s, a surge in immigration and the enforcement of compulsory school attendance laws led to exponential growth in the public schools in the United States, especially in urban areas (Chapman, 1988). To meet the needs of an increasingly large and diverse student body, school systems maximised efficiency by differentiating the school curriculum and by grouping students according to educational aptitude. By 1910, school psychologists were involved in the process of identifying children and youth at-risk for educational failure (Fagan and Sachs-Wise, 2007). Starting in the 1920s, group intelligence tests began to be used in many urban school systems to track students by instructional level (e.g. vocational or college-bound tracks; Kranzler, Benson, and Floyd, 2016). From then until the mid-1970s, the practice of testing and grouping students became a permanent fixture in American education. During that period, however, only a small percentage of children and youth with disabilities were educated in public schools. This changed dramatically in 1975 with the passage of the Education for All Children Act (P.L. 94–142). Now known as the Individuals with Disabilities Education Act (IDEA, 2004), this federal law mandates that the public school system has a responsibility to provide a free and appropriate education to all children and youth between the ages of 3 to 21 years. Eligibility for special education and related services is based on the presence of a disability that adversely affects academic performance and demonstration of a need for special education and related services. The following disability categories are used in IDEA: Specific learning disability (SLD), other health impairment (e.g. attention deficit hyperactive disorder [ADHD]), autism spectrum disorder (ASD), emotional disturbance, speech or language impairment, visual impairment (including blindness), hearing impairment (including deafness), orthopedic impairment, intellectual disability (ID), traumatic brain injury, and multiple disabilities. According to the National Center for Education Statistics (2018), in the 2014–2015 academic, year 6.6 million children and youth (13 per cent of all students) received special education and related services in the public schools.