Understanding the limited effectiveness of a whole-school relationships and sexual-health programme: fidelity of implementation, reach and acceptability of Positive Choices

Previous trials of whole-school relationships and sexual-health programmes have not reported on fidelity, reach or acceptability, despite the importance of these factors for interpreting outcomes. Our trial of the Positive Choices whole-school relationships and sexual-health programme found limited effectiveness in secondary schools in England. We aimed to understand whether sub-optimal fidelity, reach or acceptability might explain the results. A process evaluation was nested within a parallel-arm, cluster randomised-controlled trial in 49 schools from 2021 to 2025. Using staff log-books, researcher observations, student surveys and staff interviews, we assessed the delivery of the programme in 24 schools and awareness and acceptability among students, including subgroup differences. While most schools delivered lessons, fewer completed ‘whole-school components’, such as school-health promotion councils, sexual-health services reviews and student-led campaigns. No school reached a pre-defined level of ‘good fidelity’ across all components, and only 11 schools achieved ‘adequate fidelity for selected components’. Evidence of programme acceptability and awareness among students was weak, with higher awareness among sexuality- and gender-minority students, and higher acceptability among white students. Findings highlight difficulties implementing whole-school programmes focused on relationships and sexual health. More holistic whole-school programmes addressing multiple health issues, including sexual health, may be more feasible.