This study examined parenting variables as protective factors to reduce the influence of school and peer risk factors on adolescents’ aggression. Five waves of data spanning 3 years were collected from 5,581 students at 37 schools who began the 6th grade in 2001 or 2002. Class-level and perceived school norms supporting aggression, delinquent peer associations, parental support for fighting and support for nonviolence, and parental involvement were each associated with physical aggression across all waves. Each parenting variable moderated 1 or more risk factors, with the magnitude of many effects varying by gender and decreasing over time. Implications for the role parents may play in reducing the impact of school and peer risk factors for aggression are discussed.