This study investigated developmental trajectories of reading and math using latent-growth-curve analyses across multiple academic skills, measures, and multiple time periods within a single sample. Reading-related growth was marked by significant individual differences during the early elementary-school period and nonsignificant individual differences during the late elementary-school period. For math-related skills, nonsignificant individual differences were present for early math growth and significant individual differences were present in late elementary-school. No clear pattern of cumulative, compensatory, or stable development emerged for either reading-related or math skills. These differing growth patterns highlight developmental complexities and suggest domain-specific differences in achievement growth that are potentially associated with contextual factors. Educational Impact and Implications Statement Our article addresses the importance of developmental processes in reading and math. We took advantage of a large longitudinal data set to compare the similarity of developmental patterns across several reading and math skills. We found that individual differences in growth rates were greater in the early elementary school years (K-2) for reading than for math, but in later elementary school (third-fifth grades) individual differences in growth were greater for math than for reading. Our results suggest that domain-specific contextual factors may influence these developmental patterns and these differences could have important implications for the manipulation of associated contextual factors and future intervention development.