We investigated the importance of reading and mathematics achievement in the prediction of science achievement across time. By studying models of these achievement variables while controlling for important variables, such as socioeconomic status and general knowledge, a better understanding of how reading and mathematics support science achievement over time emerged. Data from Early Childhood Longitudinal Study-Kindergarten cohort was utilized as a nationally-representative and community-based sample of children across the United States. Findings provide a methodological improvement on previous literature by permitting the estimation of indirect effects, which provides the percent of the relationship accounted for at each time point. We found that reading achievement appears to significantly mediate the relationship between mathematics and science across time.