The present study investigated whether (a) growth patterns related to cognitive processing (working memory, updating, inhibition) differed in subgroups of children with reading disabilities (RD) and (b) growth in working memory (executive processing) predicted growth in other cognitive areas, such as reading and math. Seventy-three children (ages 7-17) categorized as poor decoders, poor comprehenders, or average readers were administered a battery of achievement and cognitive measures for three consecutive years. Hierarchical linear modeling showed that growth in executive processing (inhibition) in children with RD constrained growth in reading and math. The results support the notion that development in the executive system underlies performance on reading and math measures. (Contains 5 tables and 1 figure.)