Abstract: Despite a rising prevalence of mental health difficulties in the young, existing prior to, but also exacerbated by the current COVID-19 pandemic, mental health needs in this population remain unmet even in economically wealthy countries. Increasingly, supportive school environments have been suggested as having a significant impact on young people's mental health. The idea of health-promoting schools, initiated by the World Health Organisation (WHO), highlights the ongoing need for both health education via the curriculum but also a school environment that is conducive to students' health and emotional well-being. Despite this promising public health measure, existing studies into mental health-related interventions delivered in schools have been found to have a small or no effect. One explanation for this is that previous studies did not sufficiently address or focus on the school environment, which may in itself pose barriers to acceptability and successful implementation of mental health interventions. This paper will highlight a novel methodological approach to public mental health research - Participatory Action Research (PAR). The PAR method is unique in enabling study participants to become co-researchers of their own experiences in a specific context. A growing body of educational PAR research suggests that this method can also generate collaborative and participative processes foundational to positive school culture and mental health outcomes. This paper will provide an overview of such outcomes, as well as outline methodological strengths and challenges common to the PAR approach in educational mental health settings.