National Research Center on Learning Disabilities: Multimethod Studies of Identification and Classification Issues:

We normally don't think of categories of exceptionality as "successful" or "unsuccessful." But if you were asked to describe the learning disabilities (LD) category in these terms, which would you choose? One could make a good argument for its success. Consider that the Office of Special Education Programs' (OSEP) most recent data indicate that 2.72 million children between 6 and 17 years have an LD label. This number represents nearly 6% of the general population and slightly more than half of all children with disabilities (www.ideadata.org). More than 100,000 current special educators are graduates from college or university state-certified LD programs (Boe, Bobbitt, & Cook, 1997). Commercial publishers market scores of textbooks on LD, and some of these publishers, including PRO-ED and Blackwell, also produce scholarly journals devoted exclusively to the disability. The Council for Exceptional Children's Division for Learning Disabilities has 7,500 members; advocacy groups like the Learning Disabilities Association regularly lobby Congress and hold annual conferences in which more than 5,000 parents and teachers participate; and private foundations such as the National Center for Learning Disabilities have informative websites for parents of children with LD and underwrite the development of assessment tools and instructional products. From the foregoing, many would likely conclude that all is well in the LD field (see Kavale, 2001). An Ephemeral Construct All this notwithstanding, "LD" has historically been an elusive notion (Hallahan & Mercer, 2001). Two indications of its elusiveness are an absence of a coherent theory to explain the construct (e.g., Lyon, 1987; Willson, 1987) and the presence of many, and often competing, definitions and terms for it (e.g., Hallahan & Mercer, 2001). One characteristic of LD on which many researchers and more practitioners have traditionally agreed is "IQ-achievement discrepancy," the idea that the school performance of children with LD is substantially below a level predicted by their performance on an intelligence test. In other words, their poor achievement is "unexpected." However, in a series of well-publicized studies conducted in the 1990s, Fletcher, Shaywitz, Shaywitz et al. (1994), Foorman, Francis, and Fletcher (1995), Francis, Shaywitz, Stuebing et al. (1996), and Stanovich and Siegel (1994) compared poor readers with and without an IQ-achievement discrepancy on many cognitive and educational dimensions. The researchers reported few reading-related differences between the two groups, which, they claimed, invalidates IQ-achievement discrepancy as an important marker and underscores the need to develop more meaningful definitions and operationalizations of the LD construct. Despite their criticism of LD identification methods, these investigators implicitly assume "LD exists" (see Lyon, Fletcher, Shaywitz et al., 2001). Not so Ysseldyke and colleagues, who explored the provocative possibility of whether LD is little more than a fancy term for low achievement. As part of a well-known program of research, Ysseldyke and associates (e.g., Ysseldyke, Algozzine, & Epps, 1983; Ysseldyke, Algozzine, Shinn, & McGue, 1982) administered a variety of aptitude and educational tests to low achievers with and without the LD label. The researchers found considerable overlap in performance between the two groups and, partly on this basis, concluded that virtually no important educational differences exist between students with the LD label and garden-variety poor achievers. LD, they proclaimed, is little more than an "over-sophistication" of the concept of low achievement. Together with reports of dramatic variability in how individual states define LD (Frankenberger & Fronzaglio, 1991; Mercer, Jordan, Allsopp, & Mercer, 1996; Mercer, King-Sears, & Mercer, 1990) and of many teachers deliberately disregarding the definitions to ensure services for their students (e. …