How and when do peer deviant behaviours link to adolescent academic performance?: Longitudinal moderated mediation analysis using a Chinese national sample

BACKGROUND: Previous research has associated peer deviant behaviours with lower academic performance in adolescents. However, the mediation and moderation mechanisms underlying this relationship, particularly the moderating role of educational expectations, require further exploration. AIMS: This study aims to examine the longitudinal effect of peer deviant behaviours on academic performance among Chinese adolescents, as well as the mediating role of adolescents' own deviant behaviours and the moderating role of educational expectations. SAMPLE: The study utilized a nationally representative two-wave dataset from the China Education Panel Survey (CEPS, 2013-2015), including 8212 valid participants. METHODS: A moderated mediation model was constructed to test the effect of peer deviant behaviours on academic performance and the underlying mechanisms. RESULTS: Peer deviant behaviours negatively affected adolescents' academic performance over time. This relationship was mediated by adolescents' own deviant behaviours. Specifically, peer deviant behaviours increased adolescents' own deviant behaviours, which subsequently undermined academic performance. Educational expectations mitigated the impact of peer deviant behaviours on adolescents' own deviant behaviours, weakening the overall mediation effect. However, educational expectations could not mitigate the negative impact of adolescents' own deviant behaviours on their academic performance (the second stage of the mediation process). CONCLUSIONS: This study highlights the negative longitudinal effect of peer deviant behaviours on academic performance and pinpoints the stage at which educational expectations can mitigate this effect. These findings inform intervention strategies to address peer influence and foster academic success among adolescents.