Does higher peer socio-economic status predict children's language and executive function skills gains in prekindergarten?

•We examined effects of peers on children's gains in public prekindergarten.•Peer SES was associated with gains in children's language and executive function skills.•There was some evidence of threshold effects.•Findings are discussed in the context of proposals to increase preschool access.

Because most public preschool programs are means tested, children enrolled in these programs accordingly have peers from predominantly low-income families who present lower cognitive skills and more behavioral problems, on average. The present study examined the role of having a higher percentage of peers from higher-SES families on gains in children's receptive vocabulary and executive function skills at the end of prekindergarten. Participants included 417 children attending a prekindergarten program that is not means tested. Findings indicated that having a higher percentage of peers from higher-SES families showed small, positive associations with greater gains in end-of-prekindergarten receptive vocabulary and executive function skills. Results are discussed in the context of current proposals to increase access to publicly funded preschool for higher-income families.