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Since its introduction roughly 40 years ago, the special education category of specific learning disabilities has been the subject of ongoing debate and controversy. Of particular concern have been questions raised about how the disability should be defined, how to identify and serve those who have it, and the disproportionate growth the category has experienced relative to other categories of special education.

In 1969 the category of learning disability was first included in federal education legislation. That year, the General Subcommittee on Education (of the House Committee on Education and Labor) presented to the House of Representatives a bill entitled "Special Programs for Children with Specific Learning Disabilities," which was subsequently incorporated into the Elementary and Secondary Education Act Amendments of 1969. Within one year of the passage of that legislation, more than a million children had been identified as having learning disabilities.

When P.L. 94-142 was passed in 1975, the category was retained, and the resulting federal regulations contained the following definition, which was very similar to the one included in the 1969 legislation:
   Specific learning disability means a disorder in one or more of the one or
   more of the basic psychological processes involved in understanding or in
   using language, spoken or written, which may manifest itself in an
   imperfect ability to listen, think, speak, read, write, spell, or to do
   mathematical calculations. The term includes such conditions as perceptual
   handicaps, brain injury, minimal brain dysfunction, dyslexia, and
   developmental aphasia. The term does not include children who have learning
   problems which are primarily the result of visual, hearing, or motor
   handicaps, of mental retardation, of emotional disturbance, or of
   environmental, cultural, or economic disadvantage. (U. S. Office of
   Education, 1977, p. 65083)

The procedural regulations provided little guidance for how to actually identify children with specific learning disabilities (SLD), beyond indicating that a multidisciplinary team of professionals must determine that there exists a "severe discrepancy between achievement and intellectual ability" (U.S.O.E., 1977, p. 65085). Because criteria for determining such a severe discrepancy were not provided, the responsibility for establishing eligibility criteria fell to the individual states. Despite recommendations from various groups that the federal definition be replaced (e.g., National Joint Committee on Learning Disabilities, 1994: U. S. Office of Special Education Programs, 1995: Shaw, Cullen, McGuire, & Brinkerhoff, 1995), the SLD definition was retained, virtually unchanged, in the Individuals with Disabilities Education Act (IDEA), which reauthorized the federal mandate for special education services. To date, the task of operationalizing the definition has continued to fall largely to state and local education agencies,

Since P.L. 94-142 became law, the number of children classified as having SLD has increased dramatically. Between 1977 and 1994, the percentage of students identified with SLD more than doubled. In 1992-93, the 2.33 million students with SLD represented more than half (52%) of all students with disabilities in the United States (Bradshaw, 1994): however, across the states, the percentage of disabled students identified as SLD ranged from a low of about 32% to a high of over 60% (National Center for Education Statistics, 1995). This variability suggests that there continues to be disagreement over what learning disabilities are and how we should best identify them.

Since the 1969 legislation recognizing SLD as an official category, there have been numerous efforts to define (Abelman, 1992; Hammill, 1990) and operationalize (Swanson, 1991) learning disabilities. Hammill (1990) concluded that the 11 major definitions proposed since the term first came into use are actually quite similar, with the most influential ones showing substantial agreement. Mercer and colleagues (e.g., Mercer, Forgnone, & Wolking, 1976; Mercer, Hughes, & Mercer, 1985; Mercer, King-Sears, & Mercer, 1990: and Mercer, Jordan, Allsopp, and Mercer, 1996) have tracked the evolution of states' definitions and criteria over the years and have found that the overall trend has been toward increased agreement across states. Yet, despite the apparent growing consensus, state prevalence rates continue to vary widely, and questions remain about our ability to reliably differentiate students with SLD from students who have other types of learning problems. As Adelman (1989, 1992) has noted, continuing inadequacies in our diagnostic efforts have caused limited resources to be squandered and public confidence in our educational decision making to be undermined.

The present study was undertaken to newly examine the variability among the SLD terminology, definitions, and eligibility criteria of state education agencies, in part to verify Mercer, et al.'s (1996) conclusion that considerable agreement with the federal definition and procedures exists. We also attempted to identify any additional, perhaps innovative criteria and procedures in use by the states, beyond those examined in previous studies. A second goal was more exploratory in nature. Similar to a much larger study by Ysseldyke and Algozzine (1983), who applied various SLD definitions to a sample of actual cases, we applied several current eligibility models to a small number of hypothetical cases, to examine the consistency with which the cases would be deemed eligible for SLD services.


In the Fall of 1995, the education agencies of every state and the District of Columbia were contacted and asked to supply their definitions of SLD as well as their criteria for eligibility for SLD services. Thirty-nine states plus the District of Columbia responded with the requested information. (Please note that all 40 respondents are referred to as states in the remainder of this article.)

The definitions were then examined to determine the degree to which they contained the four major components of the federal definition: (1)the psychological process component, (2) the academic component, (3) the neurological component, and (4) the exclusionary component. (Because we were considering only the definition at this point, we did not check for reference to either an achievement/ability discrepancy or intelligence, as did Mercer et al. in 1996, because those components are not actually part of the federal definition. Discrepancy is addressed in the federal procedures, and intelligence is subsumed in the exclusionary clause.) A definition was judged to contain the psychological process component if it referred to SLD as a disorder of one or more of the basic psychological processes. To be counted as containing the academic component, a definition had to contain specific reference to impairment of the student's ability to listen, think, speak, read, write, spell, to do math, or some combination thereof. Definitions referring to such disorders as perceptual handicaps, brain injury, minimal brain dysfunction, dyslexia, and developmental aphasia were counted as containing the neurological component. Finally, definitions were judged to contain the exclusionary component if they specifically excluded from SLD eligibility children whose learning problems have a known primary cause such as visual or hearing handicaps, mental retardation, emotional disturbance, or environmental disadvantage. Based on these criteria, each state's definition was grouped into one of four categories: equivalent (containing all four components), variation (one component missing or one added), different (two or more components missing or added), or no definition.

In addition to comparing the state definitions to the federal definition, state criteria for eligibility were analyzed to determine whether and how states operationalize the aptitude/achievement discrepancy requirement, as well as to identify the range of additional criteria employed by the states. The investigators also examined procedural guidelines to see if states allowed for flexibility or innovation in their identification practices. Terminology used to describe the disability and its manifestations also was reviewed.

Finally, six state formulas were selected randomly from among the 24 states employing formulas. These six formulas were applied to 15 hypothetical cases, to assess the consistency with which these cases would meet the minimal, formulaic criteria for SLD services across the six states. (We acknowledge, of course, that multidisciplinary teams in states employing formulas use other data as well in determining SLD eligibility.) The hypothetical cases represented students with standard score discrepancies between their measured intelligence and academic achievement ranging from 11 to 20 points (measured by tests having means of 100 and standard deviations of 15.) Intelligence test scores ranged from 89 to 115; achievement scores ranged from 72 to 106.


Examination of the information provided by the states revealed first that there is fair agreement across states regarding the label that is applied to this category of disability. Twenty-nine of the states (73%) use the term SLD, nine (22%) simply use learning disabled, and two states (5%) refer to SLD as a perceptual or communicative disability. (All percentages reported in this section represent the percentage of all 40 states that responded.)

Analysis of the definitions revealed that 25 (63%) are equivalent to the 1977 federal definition, containing all four components. Eight (20%) are variations. all of which omit the neurological component. Thus, 83% of the reporting states' definitions are based substantially on the federal definition. Just four definitions (10%) can be classified as different (containing only two of the components), all of which leave out the neurological component as well as either the psychological process component or the exclusionary component; none of them omits the academic component. Three states provided no definitions.

In examining the states' criteria for eligibility, the investigators found that all but two of the eligibility models (95%) require the existence of a discrepancy between actual and expected achievement in one or more academic areas. Of the 38 states requiring a discrepancy for eligibility, 14 (35%) do not specify a particular formula to be used in documenting a discrepancy. Three (8%) use an expectancy formula, with the requirement that actual achievement be less than or equal to 50% of expected achievement; expected achievement is usually calculated from the student's IQ. Five states (13%) use regression formulas which typically calculate IQ/achievement score discrepancies while correcting for regression to the mean effects and (sometimes) for test intercorrelations. Only one of the reporting state's formulas does not rely on measured intelligence. Instead, eligibility is based upon the standard score discrepancy between a student's highest and lowest areas of achievement; the lowest area must be at least one standard deviation below the mean and at least 1.5 standard deviations below the highest area of achievement. The most common formula (used by 16, or 42% of the responding states) employs simple standard score differences between measured intelligence and achievement. Even among those states, however, there is variability. Five require a discrepancy of at least one standard deviation; another five require 1.5 standard deviations; and the remaining six states have some other standard score discrepancy requirement. The one model that distinguishes among mild, moderate, and severe discrepancies provides incremental discrepancy requirements, with corresponding intervention recommendations. Only one state provides separate discrepancy requirements for younger and older children.

It was found that a large number of states consider a child's prior educational experiences in determining SLD eligibility. Seventy-two percent of the responding states exclude a child from consideration if the learning problem is judged to be due to the learning environment. Of these 29 states, however, only 11 (28%) require that interventions or adaptations of teaching strategies be tried prior to making a formal referral. The remaining 18 states (45%) simply require that the child has been exposed to "conventional" or "appropriate" teaching methods.

Another factor considered by some states is the degree to which a child's academic achievement is characterized by significant variability, with higher performance in some areas and markedly lower performance in others. Two states (5%) specifically require evidence of such variability. Twenty-nine (73%) simply require that the child's deficits be in "one or more" of seven basic academic areas, and two states require that deficiencies be evident in "two or more" basic academic areas. The remainder (seven states) make no mention of the distribution of academic difficulty.

Finally, the degree of flexibility in the identification process was another variable on which states differed. As indicated previously, 16 states did not report the use of any type of discrepancy formula, relying solely on the judgment of their multidisciplinary teams to determine eligibility. Of these 16 states, three (8%) provide no criteria at all--only a definition of SLD. Of the 24 states that do specify a discrepancy formula, 19 (48%) allow for innovation at the local level; for example, the local multidisciplinary team may employ alternate documentation strategies if a student does not meet the formulaic criteria but appears to manifest a significant achievement/intelligence discrepancy.

When six randomly selected eligibility models were applied to 15 hypothetical cases, the case outcomes were notably variable. There was unanimous agreement on only four of the cases, all of which were judged not eligible for SLD services; each of these had an aptitude/achievement score discrepancy of less than one standard deviation (15 points). Three cases with discrepancies of exactly one standard deviation were eligible under only one of the six models. The seven cases that had discrepancies ranging from 16 to 19 standard score points (greater than one standard deviation but less than 1.33 standard deviations), were eligible under two of the six models. The remaining case, with a discrepancy of 20 points (1.33 standard deviations), was eligible under four of the six models employed.


Our examination of states' SLD definitions and criteria leads to a number of conclusions. First, at least among the 40 states that responded, there is considerable agreement regarding what this category of disability should be called. The vast majority of states use the term SLD. These results suggest improved consensus since 1989, when Chalfant determined that state education agencies were using five different terms for the disability: learning disabled, learning disabilities, specific learning disabilities, perceptually impaired, and perceptual communication disorder.

Fairly substantial consensus also is apparent in the definitions employed by the reporting states. Similar to Mercer et al.'s (1996) findings, these results show that a large majority of states use a definition identical to or only slightly different from the federal definition. Not surprisingly, all of the states' definitions refer to specific academic deficits as characteristic of SLD. There is considerably less consensus, however, with regard to the other components of the federal definition. Again consistent with Mercer et al.'s findings, the neurological component is the one most frequently absent from the states' definitions (although their findings did suggest its inclusion was on the rise.) That this component of the federal definition is most frequently absent from states' definitions is not too surprising, given the complexity, expense, and in many cases impossibility of ascertaining a neurological basis for SLD. Some states may eliminate this component in order to emphasize an educational as opposed to a medical conceptualization of the disability. However, as Mercer et al. speculated, our rapidly growing understanding of how neurological factors impact learning may result in increased emphasis by states on this component in the future. Presently, however, citing such conditions as minimal brain dysfunction and developmental aphasia as examples of SLD likely provides little clarification for most users of the definition and probably increases rather than decreases uncertainty among those making educational eligibility decisions.

Despite the improved agreement regarding the category label and definition, there continues to be notable variability from state to state in how SLD eligibility is determined. Although there is nearly unanimous agreement across states that SLD is manifested in a discrepancy between the individual's actual academic achievement and potential for achievement, the states differ dramatically in how this discrepancy is to be documented. The majority provide specific, though widely varying, formulaic criteria, but a large number of states offer no guidelines at all. These findings raise several related concerns. First, the variability across states likely results in inequities in federal and state funding and limits the comparability of different states' SLD populations for research purposes. Another even more worrisome concern is that this variability allows for the possibility that a child who is found eligible for SLD services in one state may be ineligible upon moving to a different state. Such a turn of events is not only unfair and potentially injurious to the child, it also undermines the credibility of the professionals involved and, indeed, public education in general, outcomes we can ill afford. An additional concern relates to the continued, prevalent use of discrepancy formulas in the identification process, despite long-standing arguments that virtually all such formulas are inherently flawed (Reynolds, 1985; Telzrow, 1985.) Unfortunately, lingering uncertainty over what learning disabilities are and how we should identify them has led to reliance on procedures that are at least clear and specific, if not psychometrically defensible.

Although a large majority of states endorses the exclusion from SLD eligibility of children whose learning problems can be traced to their prior educational experiences, very few mandate the implementation of instructional interventions prior to or during the identification process. Thus, one form of environmental disadvantage--ineffective educational practices--is effectively eliminated as an exclusionary factor. As a result, school personnel in most states are free from the burden of having to consider that a student's failure to achieve as expected lies not within the child but within the educational environment itself.

Across the states, criteria for eligibility are generally quite flexible. Even states that utilize very specific formulas typically allow for the use of alternative strategies and professional judgment and innovation in determining SLD eligibility. There are advantages and disadvantages inherent in such flexibility. The primary advantage is that competent professionals are not bound by rigid adherence to arbitrary formulas or rules; rather they can determine best practices on a case-by-case basis and exercise well-informed judgment in making eligibility decisions. However, as Hammill (1990) has pointed out, unless such professionals operate from a clear conceptual understanding of what the disability is, and is not, their decisions may not be sound. Furthermore, in the absence of clearly operationalized criteria, state and local decisions about assessment and eligibility are likely to be especially subject to political and financial considerations and to the personalities and varying levels of experience, interest, and professionalism of the decision makers. As a result, those decisions may not always reflect the best interests of the children who are affected by them.

Unless the forthcoming IDEA procedures provide substantially more specific guidelines than have been provided in the past, we are likely to continue to see considerable variability in how children are evaluated and who is found eligible for special education services. As Shaw, et al. (1995) have suggested, our lack of diagnostic rigor and consistency is likely to become even more problematic over time, due to demographic trends that may result in increased demands for special education services. Educators are likely to face even greater pressure "to more clearly distinguish those who are truly disabled from those who are not." (Shaw, et al., 1995, p. 586.)


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