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Poor readers who met low achievement and IQ-discrepancy definitions of reading disability were compared with nonimpaired readers on their development of eight precursor and reading related skills to evaluate developmental differences prior to students' identification as reading disabled. Results indicated no evidence for differences between the two groups of poor readers in the development of the eight skills, with three exceptions. Students in the IQ-discrepant group demonstrated greater growth in letter sound knowledge, greater mean performance in visualmotor integration at the beginning of first grade, and greater deceleration in rapid naming of letters. When compared to the nonimpaired group, low-achieving readers demonstrated poorer performance and development in all skills, while the IQ-discrepant readers demonstrated poorer performance and development in phonemic awareness, rapid naming of letters and objects, spelling, and word reading. The largely null results for comparisons between the two groups of poor readers challenges the validity of the two-group classification of reading disabilities based on IQ-discrepancy.