Attention deficit/hyperactivity disorder (ADHD) is a chronic condition that is thought to affect from 3% to 5% of school-age children in the United States (American Psychiatric Association, 2000). Now one of the most commonly diagnosed childhood disorders (Barkley, 1998), ADHD is estimated to affect approximately 2 million school-age children (Forness & Kavale, 2002). These children experience difficulties in behaviors crucial to academic success, such as maintaining attention, modulating activity levels, inhibiting impulsive responses, and persisting with academic tasks (DuPaul & Stoner, 2003). Because of their large numbers and refractory behaviors, children with ADHD present a challenge for the school system.
Many children with ADHD qualify for accommodations and/or services under Section 504 of the Vocational Rehabilitation Act or the Individuals With Disabilities Education Act (IDEA; Reid & Katsiyannis, 1995). Estimates are that more than half of children with an ADHD diagnosis are school-identified as eligible for services under IDEA (Barkley, 1998; Reid, Maag, Vasa, & Wright, 1994). Most of these children are served under the categories of learning disability (LD), emotional disturbance (ED), or other health impairment (OHI). Some students with ADHD and a co-occurring cognitive impairment are served under the mental retardation (MR) category (Abikoff, 2002), and those with expressive and/or receptive language limitations are served in the speech-language impairment (SLI) category.
Although ADHD has been the subject of a tremendous amount of research attention (Reid, Maag, & Vasa, 1994), relatively little research has been conducted on ADHD among students receiving special education in the schools. Forness and Kavale (2002) have identified four major questions of interest regarding these students: (1) What is the prevalence of ADHD among students served in special education? (2) Under what categories are students with ADHD served by special education? (3) In what settings are these students served? (4) What services are they provided? The following sections summarize the current literature on these questions as background for presenting new findings related to each of them.
PREVALENCE OF ADHD AND SPECIAL EDUCATION ELIGIBILITY
Many studies have focused on the extent to which children with ADHD theoretically would meet diagnostic criteria for an IDEA disability category; however, this focus does not address the question of the number of children with ADHD who actually are served under IDEA. Further, data on the extent to which children with ADHD are served in various disability categories are sparse (Forness & Kavale, 2002). Gaining a clear picture of the prevalence and category distribution of students with ADHD receiving special education is further complicated by the fact that the diagnostic criteria for ADHD have changed three times since 1980, resulting in the use of slightly different definitions of ADHD over time.
OTHER HEALTH IMPAIRMENT
OHI is the main special education category under which students with ADHD who have no coexisting disabilities may be served. In 1991, the category was opened to children with ADHD based on the "limited alertness" language in the definition (Davila, Williams, & MacDonald, 1991). The intent was to provide a means for serving children with ADHD who would not otherwise qualify for special education services.
Few data have been available on the prevalence of children with ADHD in the OHI category because states do not report the specific disabilities of children in it. Forness and Kavale (2002) noted that the increase in children identified under the OHI category exceeds that for other categories of disability; they estimated that children with ADHD accounted for 68% of new students identified in the OHI category in the 4 years before their study. …