A study examined the performance on the Kaufman Assessment Battery for Children (K-ABC) for first grade students from a rural northwestern school who had received reading instruction via a structured, phonics-based reading program. Specifically, the study compared the performance of (1) three students scheduled for retention because of poor reading progress, (2) three students matched on ability with the retention group by their first grade teachers but reading acceptably, and (3) a random sample of five average readers. All students completed the K-ABC, an individually administered aptitude test that assesses sequential and simultaneous processing ability as well as academic achievement. Results showed that students who had difficulty with reading tended to perform more poorly on the K-ABC than did average readers. The findings suggest that educators need to consider adapting primary reading instruction in relation to cognitive task performance. (The paper contains 21 references and several tables of data.) (FL)