Academic journal article School Psychology Review

Severe Discrepancy Models: Which Best Explains School Identification Practices for Learning Disabilities?

Academic journal article School Psychology Review

Severe Discrepancy Models: Which Best Explains School Identification Practices for Learning Disabilities?

Article excerpt

Abstract. This study examined which of three types of severe discrepancy approaches--intraindividual achievement discrepancy, absolute achievement discrepancy, or relative achievement discrepancy--best accounted for students' identification as learning disabled (LD). Participants were 48 fourth-grade, school-identified LD students from a high-achieving and a low-achieving school district in Minnesota. Students were tested with a short form of the WISC-III and two measures of reading, and the resulting discrepancies were matched to students' school LD classification. Results showed that the best explanation for school-based LD identification practices was a relative achievement discrepancy, with between 85-95% of LD students in both districts identified accurately. The state-mandated ability-achievement discrepancy accounted for only 60% of LD students. Implications of these findings for LD identification practice based on an ecological perspective are discussed.


Every day in the United States, many school psychologists are engaged in a process of identifying students as eligible for special education under the category of learning disabilities (LD). Almost one-half of school psychologists report spending more than 40% of their time in this process (Ross, 1995).

LD identification is most commonly based on the administration of an ability measure and subtracting from that obtained score the student's score on an achievement test (Berninger & Abbott, 1994). This approach is predicated on the idea that the learning disability is "within the student" or what in this article will be called an Intra-Individual Achievement Discrepancy (IAD). Others (e.g., D. Fuchs, L. Fuchs, Mathes, & Lipsey, 2000; Ysseldyke & Algozzine, 1983) have criticized the IAD and suggested that the defining feature of LD is severe low achievement alone or what will be referred to herein as an Absolute Achievement Discrepancy (AAD). A third approach has criticized both the IAD and AAD discrepancy types as inadequate and suggested LD identification is based on a severe achievement discrepancy from a local achievement standard (Deno, 1989; Shinn, 2002). This model will be referred to as a Relative Achievement Discrepancy (RAD).

Intra-Individual Achievement Discrepancy (IAD)

The widespread application of the IAD approach can be attributed to the definitional language of the Individuals with Disabilities Education Act (IDEA), where learning disabilities are based principally, but not entirely, on "a severe discrepancy between achievement and intellectual ability" (U.S. Office of Education, 1977). Nearly all states base their own specific definitions and identification regulations on an IAD (Frankenberger & Franzaglio, 1991; Mercer, Jordan, Allsop, & Mercer, 1996) through one of two forms: (a) a simple discrepancy, where the difference score is used for decision making, or (b) a regression discrepancy, where regression to the mean and measurement error are taken into account by transforming the obtained scores mathematically. However, few states use the same simple or regression discrepancy approach and across states there is a high degree of variability in the magnitude of the discrepancy that must be obtained to be considered severe. Additionally, although federal regulations pre clude identification through application of a severe discrepancy formula alone, the preponderance of evidence indicates that the ability-achievement discrepancy is the defining feature in practice (Frankenberger & Harper, 1987; Ross, 1995; Stanovich, 2000).

Regardless of the IAD approach or the criterion that defines a discrepancy as severe, the LD identification practices within a state would be expected to identify the same students as LD. For example, a student who has a learning disability in San Francisco would be expected to have a learning disability in Sacramento, San Diego, or Fresno, and achievement context should not have an effect. …

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