Using a longitudinal, UK representative sample from the Millennium Cohort Study, the present study examined the effects of socio-economic factors on mother-and teacher-rated behaviour, and the unique and cumulative contribution of both risk and protective factors inherent in children's proximal and distal influences to behaviour during the toddler years and at school entry. The findings showed that although family income, parental employment and maternal education had a significant moderate impact on child problem behaviour as rated in the home and school, when considered in the context of child characteristics and family processes their contribution was negligible, especially for income. In contrast, parenting practices and parental well-being emerged as good predictors of behavioural difficulties and prosocial behaviour at school entry, pointing to the importance of supporting parents in order to promote social competence in young children. These findings have implications for family policy.