This study examined the links between classroom skill compositions and preschoolers' early learning and development in the nationally representative Head Start Family and Child Experiences Survey 2014 (FACES, n = 1,711 children/207 classrooms) and public pre-K programs in a county in Virginia (n = 1,467 children/123 classrooms). Results from a series of covariate-adjusted multilevel regression models revealed that there were small within-domain associations between classmates' skill mean and individual children's academic and executive function skill development in FACES, but not in the Virginia data. There were no consistent associations across skill domains nor as a function of classmates skills' heterogeneity. In addition, we found little evidence that these associations between classroom skill compositions and individual children's development varied by children's initial skill levels, family income, maternal education, and home language. When taken together, these findings inform the discourse on peer influences on children's learning in early childhood.