This study examined heterogeneity in change in reading test scores and attention problems during middle childhood and whether heterogeneity in change in these variables predicted later problem behavior. Our sample consisted of 783 students recruited from 10 Pacific Northwest schools. For both reading scores and teacher report of attention problems, latent growth curve models of annual data from Grades 3 to 6 showed statistically significant heterogeneity in initial level and change. Level and change factors for both variables were statistically significant predictors of problem behavior in 7th grade. In a combined model that included growth factors for both reading and attention problems, only level of attention problems had a unique and statistically significant association with problem behavior.