<p>The transition from kindergarten to primary school marks a crucial phase in children’s development, in which parental involvement significantly affects children’s smooth transition. However, existing research frequently focuses on the developmental outcomes of such a transition on children, overlooking the significance of parental educational cognition about learning, life and social development and their behaviors during this critical period. Using a random sampling methodology invited 1437 parents to participate in a survey assessing their socioeconomic status, cognition, behaviors related to over-prepared education, and social adaptation during transitions. Eventually, two simple mediation models were established. The results suggest that family SES significantly positively predicted social adaptation involvement during kindergarten-primary school transitions. Furthermore, parents’ over-prepared cognition fully mediated the relationship between family SES and their kindergarten education-related behaviors during transitions, whereas social adaptation cognition partially mediates the relationship between family SES and their social adaptation behaviors. These findings highlight that family SES is a significant predictor of parental involvement during early childhood education transitions and that parental educational cognitions play a different role in the link between family SES and parental involvement.</p>