Dating and relationship violence (DRV) among young people is widespread. DRV is associated with subsequent mental ill health, substance use and sexual risk among girls and boys and is a leading cause of morbidity and mortality among girls globally. Harmful social norms are widely recognised for their role in sustaining DRV, and interventions often seek to change these. However, little evidence is available to suggest which specific norms are most salient and where protective norms might be strengthened. We conducted, audio-recorded and transcribed consultations and semi-structured interviews with students (years 9 and 10), school staff and parents/carers from ten secondary schools in England. We also audio-recorded discussions in staff DRV trainings in four of these schools. Data collection took place between April 2017 and July 2018. This research explored participant accounts of social norms relating to gender and to DRV in schools and their influence on DRV behaviours. Drawing on Giddens' structuration theory, our thematic analysis found that sexist social norms subjugating girls to boys facilitated gendered practices of harassment and abuse, including DRV; and that these practices, in turn, reproduced this gendered power structure. Our data suggest that while physical DRV is socially proscribed, norms supporting controlling behaviours and inhibiting disclosure of victimisation directly underpin DRV. They further suggest that indirectly, gender norms concerning cross-gender friendships; sexual harassment; the policing of girls' sexuality; homophobic abuse; and dominance, control and sexual activity as masculine ideals indirectly sustain DRV. Accounts demonstrated that students and staff challenge harmful norms, but that these efforts can be ineffective and socially punished. Our findings can inform DRV interventions, which should draw on evidence to foster protective norms and shift those that sustain DRV.