Parental involvement (PI) in their children's schools has been shown to have a positive influence on the children's behaviours and academic achievement. The purpose of this study was to examine predictors of PI and relations of PI in schools to child externalizing and internalizing behaviours. Data were from the fifth-grade wave of the Early Head Start Research and Evaluation Project, with 1354 fifth grade low-income children and parents. Results revealed that family conflict predicted child internalizing and externalizing and negatively predicted PI in schools. However, PI in schools partially reduced the negative effect of family conflict on both internalizing and externalizing. Parental warmth negatively predicted child externalizing behaviours, and positively predicted PI in school. Additionally, PI in schools further enhanced the positive effect of parental warmth in reducing externalizing behaviours. The study highlights home and parent characteristics that relate to low-income fifth-grade parents' involvement in their child's education and demonstrates the mediating role of PI in reducing behavioural problems of low-income children.