Abstract Given well‐established links between socio‐economic adversity and mental health, it is unsurprising that young people's mental health is deteriorating amidst economic crises. The World Health Organisation (WHO) recognises mental health as “crucial to personal, community, and socio‐economic development” and outlines goals to reshape environments such as schools to protect mental health. Schools offer an ideal setting to promote wellbeing and prevent mental ill‐health during a key developmental window. We describe how social inequalities present a challenge to designing school‐based interventions for prevention and promotion for mental health and wellbeing, and suggest priorities to aid and evaluate their effectiveness.