This paper explores the issue of harmful sexual behaviour (HSB) presented by young people, advocating a preventative approach through an increased focus on primary education. The definition of HSB, contributing factors and recent prevalence among young people is discussed. Much of the research and policies explored relate directly to England and the UK, however the advocated approaches and conclusions have an international relevance. The paper establishes the damaging impacts of HSB on young people and teachers, demonstrating the serious need for action across the education system. A preventative approach advocating the important role of primary education in reducing HSB and peer on peer abuse is presented, exploring three key areas: education, pastoral support and staff support. Policies and practices comprising such an approach are critiqued, and their relevance to primary education established. The need for future research into the needs of primary education and the prevalence of HSB in pre-secondary education is identified.