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Journal Issue: Special Education for Students with Disabilities Volume 6 Number 1 Spring 1996

Identification and Assessment of Students with Disabilities
Daniel J. Reschly

Identification and Assessment


The two main purposes of identification and assessment of students with disabilities are to determine whether they are eligible for special education services and, if they are eligible, to determine what those services will be.

Eligibility for special education services requires two findings: first, the student must meet the criteria for at least one of the thirteen disabilities recognized in the federal Individuals with Disabilities Education Act (IDEA) or the counterparts thereof in state law,1,2 and second, special education and/or related services must be required for the student to receive an appropriate education.2,3 It is true that some students are eligible for special education and/or related services but do not need them, while other students need the services but are not eligible according to federal or state classification criteria.

If the disability diagnosis and special education need are confirmed, the student then has certain important rights to individualized programming designed to improve educational performance and expand opportunities. These rights are established through several layers of legal requirements based on federal and state statutes, federal regulations, state rules, and state and federal litigation.2

Chief among these rights are the requirements that eligible students with disabilities must receive an individualized educational program (IEP) based on needs identified in an individualized, full, and complete evaluation. The needs identified during the evaluation form the basis for the student's personal and educational goals, the specially designed instruction and related services (for example, psychological consultation or physical therapy), and the methods to evaluate progress toward the student's goals.

The classification system used in special education identification also serves numerous other functions that are not discussed here (for example, organization of research; communication among scholars, lay public, and policymakers; differential training and licensing of specialists such as special education teachers; and advocacy for expanded rights and support for programs).

Current Practices

A number of comprehensive classification systems exist and influence, to varying degrees, classification in special education.4-6 There is, however, no official special education classification system that is used uniformly across states and regions. For statistical purposes, students are classified by their primary disability, though it is not unusual for a student to have disabilities in more than one category.

Federal and State Disability Categories

Thirteen disabilities are briefly defined in the federal IDEA regulations: autism, deaf-blindness, deafness, hearing impairment, mental retardation, multiple disabilities, orthopedic impairment, other health impairment, serious emotional disturbance, learning disability, speech or language impairment, traumatic brain injury, and visual impairment. Federal law does not provide classification criteria for any of these disabilities except learning disability.1

These disability categories are based to varying degrees on eight dimensions of behavior or ability: intelligence, achievement, adaptive behavior, social behavior and emotional adjustment, communication/language, sensory status, motor skills, and health status.7 About 90% of the students who are found eligible for special education have disabilities that fall primarily within the first five of those dimensions.

Although all states must provide special education to all students with disabilities, states may or may not adopt the disability categories recognized in the federal regulations. In fact, there are significant differences across the states in the categorical designations, conceptual definitions, and classification criteria.8,9 These differences have their greatest impact on the students who will be described later as mildly disabled. It is entirely possible for students with identical characteristics to be diagnosed as disabled in one state, but not in another, or to have the categorical designation change with a move across state or school district lines.

The category of mental retardation (MR)10 illustrates the diverse classification practices in special education. The IDEA regulations define mental retardation as "significantly subaverage general intellectual functioning existing concurrently with deficits in adaptive behavior."1 Mental retardation has been recognized as one of the disabilities for which special education was provided throughout this century.6,11 Despite the longevity and nearly universal recognition of this category, enormous differences exist among states in terminology,10 key dimensions (for example, some states do not include adaptive behavior in the conceptual definition), and classification criteria (for example, the intelligence quotient [IQ] "ceiling" for this category varies from 69 to 85). The variations in criteria have the most effect on the mild level of mental retardation. Similar variations among states exist for other disability categories, especially serious emotional disturbance (SED), learning disability (LD), and speech or language impairment (SP/L).

Medical and Social System Models

Historically, the special education classification system involved a mixture of medical and social system models of deviance.7-9 The least ambiguous disabilities are the clearly medical disabilities (such as visual impairment or orthopedic disabilities), often recognized by the child's physician soon after birth or during the preschool years. In contrast, the disabilities defined by social system models represent behavior, intelligence, communication abilities, or other characteristics that deviate significantly from the norm, and which are generally diagnosed during the school years (see Table 1). The initial identification of a student with social system disabilities usually occurs because of a teacher-initiated referral of the child as a result of severe and chronic achievement or behavioral problems.7

In the social system model, the question of where to draw the line between normal and "significantly different" characteristics is somewhat subjective, and has properly been considered a matter within the discretion of local or state authorities. (See the article by Parrish and Chambers in this journal issue.) In addition, knowledge about the possible underlying physical causes of some social system disabilities (such as learning disabilities and attention-deficit disorder) is changing rapidly. There is research linking biological factors to mild disabilities such as learning disability, and in particular reading disabilities. (See the article by Lyon in this journal issue.) These links involve possible differences in brain functions among readers with and without disabilities as well as a possible genetic link to severe reading disabilities. The differences are, however, correlational as noted by a writer in a recent Science News and Comment.12 Further research is needed to determine (1) if these biological correlates are replicated with new samples of students with learning disability; (2) whether the presence or absence of the correlates reliably distinguishes between those with and without learning disability; and (3) whether treatments work differently depending on the presence, amount, and kind of biological correlates. Until these questions are answered, little practical utility exists for the research on the biological correlates of learning disability.

Mental retardation is perhaps the clearest example of the mixture of medical and social system models. The current prevalence of mental retardation among school-age children and youth is 1.1%.13 Approximately one-half of these persons have moderate to severe disabilities (IQ below 55) characterized by identifiable anomalies (such as Down's Syndrome) that are the cause of their significantly lower performance in adaptive behavior and intelligence.6,11 A second group of persons with mental retardation who typically perform at the mild level (IQ about 55 to 70 or 75) do not exhibit any biological anomalies that can be posited as the cause of their lower performance.14,15 Indeed, the etiology of this form of mental retardation has been called cultural-familial or psychosocial as a means of acknowledging that social system factors may be preeminent.16 Persons with mild mental retardation rather than moderate or severe mental retardation have markedly different levels and patterns of educational needs and adult adjustment. Unfortunately, the current classification system uses the same term to refer to both groups of persons,5 leading to frequent confusion over what mental retardation means and unnecessary stigmatization of persons with mild mental retardation.6

The paucity of clear evidence of a medical basis for many disabilities and the fact that most disabilities are at the mild level (see later discussion) does not diminish the importance of early recognition of problems and the implementation of effective treatments. For example, problems with attaining literacy skills as reflected in very low reading achievement or poor behavioral competencies as reflected in aggressive behaviors often interfere significantly with normal development and seriously impair the individual's opportunities to become a competent, self-supporting citizen.