Longitudinal Stability of LD Subtypes Based on Age- and IQ-Achievement Discrepancies

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Abstract
A twofold classification system based on discrepancy formulas was employed to subtype normal (NLD) and learning disabled (LD) children into educationally meaningful groups based upon simultaneous consideration of IQ-achievement and age-achievement discrepancies. 52 LD and 58 NLD children were classified into five groups: overachievers, target achievers, underachievers, slow learners, and disabled achievers. This classification system appeared useful by its ability to differentiate disabled learners, who were discrepant in reading achievement as predicted by both age and IQ, from slow learners, who were only discrepant in reading achievement as predicted by age. The longitudinal stability of the classification scheme was examined over a 3-year period. As expected, NLD students' achievement was more predictable over time than their LD peers' LD students became more disabled with age in spite of remedial services. The educational implications and theoretical relevance of discrepancy-based subtypes are discussed.