Using data from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development (NICHD SECCYD), we used 2-level random effects models to examine whether the quality of school and home environments during elementary school moderated associations between pre-K quality and math, reading, and vocabulary achievement from first through fifth grade. Results showed that the quality of the home environment moderated the association between pre-K quality and children's vocabulary achievement. Supportive home environments during elementary school had an additive effect over and above the positive effects of pre-K quality in predicting children's vocabulary achievement. In contrast, when children experienced high levels of pre-K quality and lower quality home learning environments, the positive effects of pre-K were less likely to be sustained. Findings suggest the importance of considering programs and policies to support home-based learning as one potential mechanism to sustain early effects of pre-K. (author abstract)