Beyond the sandbox: Lasting associations of preschool peer language skills with third-grade vocabulary and the role of primary school peers

While emerging evidence links peer group composition to children's language development, most studies are limited to short-term effects and rarely examine potential long-term patterns across educational stages in which children encounter different peer groups. This study examined whether the average language skills of preschool peers showed a lasting association with children's receptive vocabulary in third grade, and further explored whether subsequent primary school peer groups added to or moderated this association. Using data from the German National Educational Panel Study (NEPS; n = 499 target children in 213 preschool groups and 190 primary school classrooms), we applied multilevel regression analyses accounting for children's baseline vocabulary, sociodemographic characteristics, and the nested structure of the data. Preschool peer language skills showed a modest positive association with later vocabulary, which was moderated by primary school peer group skills. Contrary to expectations, preschool effects were strongest when children entered lower-skilled primary school peer groups and were not detectable in higher-skilled groups. No independent additive effect of primary school peer skills emerged. These findings suggest that preschool peer groups may serve as a compensatory foundation when later peer environments are less supportive and underscore the importance of considering consecutive peer contexts when examining longer-term associations in language development. • Preschool and primary school peer contexts jointly predicted third-grade vocabulary. • Preschool peer effects depended on subsequent peer group language levels. • Preschool peer effects were most evident in lower-skilled later peer groups. • Findings highlight the importance of considering successive peer environments.