This study examined the reading and math achievement profiles and longitudinal growth trajectories of a nationally representative sample of children ages 6 through 9 with an ASD. Four distinct achievement profiles were identified: higher-achieving (39%), hyperlexia (9%), hypercalculia (20%), and lower-achieving (32%). Children with hypercalculia and lower-achieving profiles were more likely to be from low socioeconomic families and had lower functional cognitive skills than the higher-achieving profile. All four profiles lost ground in passage comprehension over time. Slower improvement occurred for the higher-achieving group on letter-word identification, the hyperlexia group on conversation abilities, and the hypercalculia group on calculation and functional cognitive skills relative to the lower-achieving group. [This paper was published in "Autism: The International Journal of Research and Practice" v19 n2 p200-210 Feb 2015 (EJ1050972).]