Using four-wave longitudinal reading and mathematics data (4th to 7th grades) from a large urban school district, growth curve modeling was used as a tool for examining three research questions: Are achievement gaps closing in reading and mathematics? What are the associations between prior-achievement and growth across the reading and mathematics domains? Is there an association between the receipt of additional services (special education, English-as-second-language, free and reduced lunch program) and reading and mathematics achievement? Results showed that rates of growth in achievement diminished over time and achievement gaps closed in reading, but not mathematics. Reading ability was directly related to gains in mathematics. Analysis of the time-varying covariates showed that there tended to be positive effects of the receipt of English-as-second language instruction on both reading and mathematics achievement, whereas students receiving special education and free and reduced lunch programs consistently had lower academic achievement levels. Implications for the achievement literature are discussed. (Contains 5 tables and 3 figures.)