Using data from the National Institute of Child Health and Human Development's Study of Early Child Care and Youth Development, this study examined the cross-lagged relations between behavioral engagement and reading achievement in elementary school and whether these cross-lagged relations differed between low-socioeconomic status (SES) and mid- or high-SES students. Students' behavioral engagement and reading were assessed in preschool, 1st grade, 3rd grade, and 5th grade. Results showed that reading achievement in preschool predicted subsequent behavioral engagement in 1st grade and reading achievement in 3rd grade predicted subsequent behavioral engagement in 5th grade. However, behavioral engagement did not significantly predict later reading achievement. Furthermore, although the relationship patterns between reading achievement and subsequent behavioral engagement were the same across the 2 groups, the strength of relations was stronger for low-SES students.