The SHARE study, launched in 1994, was designed to improve young people’s sexual health through a comprehensive, school-based sex education programme. The project had three core components: • Development of a theoretically grounded, teacher-delivered curriculum focused on sexual health and relationships • Rigorous evaluation of the programme via a randomized controlled trial and process evaluation • Primary research into young people’s sexual behaviours, relationships, and the broader social influences shaping them At baseline, 7,616 pupils aged 13 to 20 participated. Data collection included face-to-face and postal questionnaires conducted between 1994 and 2002, with additional data linkage continuing until 2006. For further details, the study is registered with ISRCTN: ISRCTN48719575, and a cohort profile is available via the BMJ Open Access Repository. This data is identifiable.