Macdowall W, Jones KG, Tanton C, Clifton S, Copas AJ, Mercer CH, et al. Associations between source of information about sex and sexual health outcomes in Britain: findings from the third National Survey of Sexual Attitudes and Lifestyles (Natsal-3). BMJ open. 2015:5(3). https://doi.org/10.1136/bmjopen-2015-007837. The School of Health and Life Sciences is committed to the pursuit of excellence in teaching, research and knowledge transfer across the disciplines of health, nursing and social care, biological and biomedical sciences, psychology and vision sciences. We still have a long way to go. This is an emotional evening for the families who received their loved ones tonight," he said.

Would students voted as ‘influential’ be willing to take on and fulfil the peer supporter role? [acceptability; progression criteria 1, 2b in Table 2]Teachers in position to compare STASH with school SRE (about half the sample) generally saw it as offering an update to out-of-date materials. The relatively relaxed STASH environment was also highlighted as facilitating ‘sensible questions […] about risk-taking behaviour’. One teacher reflected: ‘they certainly wouldn’t ask me those questions’. (Teacher, source 6).

Valente TW. Network interventions. Science. 2012;337(6090):49–53. https://doi.org/10.1126/science.1217330.All students in the intervention year group were eligible for selection as Peer Supporters; however, only those nominated as ‘most influential’ by their peers were invited to recruitment sessions. Individual informed written consent was obtained for the Peer Supporter role. Programme theories provide a framework for understanding implementation uncertainties and should be continually refined as feasibility work progresses. The evolution from the intervention implementation stage (Supplementary material one) to analysis of findings (Fig. 1) reflects learning from the process evaluation. Together, the data described above largely confirmed that the programme theory adequately captured the conditions of success for STASH and that these conditions were largely met, albeit with variation across schools. In terms of the hypothesised mechanisms of change, our data largely confirmed these with a few exceptions. We envisaged that social validation would be a key mechanism (supplementary material). In practice, we found that the Peer Supporters did not appear to be socially validated in their role (they were neither validated nor disapproved of), yet the role still appeared to enhance self-esteem and wellbeing. Thus, we removed this mechanism from the final programme theory (Fig. 1). Being nominated as an influential peer was a key mechanism in generating Peer Supporter confidence and self-esteem, confirming additional benefit of peer-nomination over other social network criteria (e.g. selecting individuals that optimally span the network) [ 27, 44]. Our finding that it was difficult for Peer Supporters to generate high levels of engagement among non-Peer Supporters prompted reflection on whether it was realistic to expect the Peer Supporters to generate intrinsic motivation to engage with the intervention among their friends and whether this was a key mechanism of change; this mechanism was also removed. It is possible that information and norm change could still diffuse through a network without overt individual online engagement by Peer Supporter friends, although this remains an uncertainty. Were study progression criteria met? Gale NK, Heath G, Cameron E, Rashid S, Redwood S. Using the framework method for the analysis of qualitative data in multi-disciplinary health research. BMC Med Res Methodol. 2013;13(1):1–8. https://doi.org/10.1186/1471-2288-13-117. Tolli MV. Effectiveness of peer education interventions for HIV prevention, adolescent pregnancy prevention and sexual health promotion for young people: a systematic review of European studies. Health Educ Res. 2012;27(5):904–13. https://doi.org/10.1093/her/cys055.