BackgroundThe school environment offers an ideal opportunity for early identification and intervention for youth with self-harm and complex mental health issues, such as borderline personality disorder (BPD). Yet, class teachers often report minimal knowledge, feeling ill-equipped to respond, and experience high levels of stress when exposed to such challenges. Research is required to understand how training and development activities led by school counsellors may enhance teacher attitudes, confidence and knowledge of self-harm and complex mental health issues, such as BPD. We aimed to explore the extent that a whole of school initiative might enhance capacity for early identification and intervention.Method18 secondary schools implemented a manualised program, Project Air Strategy for Schools. N = 400 class teachers (71.3% female, mean age 42 years) across city and rural locations were evaluated before and after program implementation on attitudes, knowledge and skills.ResultsProviding class teachers with additional training on complex mental health issues and associated behaviours such as self-harm was well received. Participants reported post-program improvements in their optimism (d = .35), confidence (d = .63), knowledge (d = .73) and skills (d = 0.67) in working with young people with complex mental health issues, such as BPD.ConclusionsProviding school counsellor led structured approaches, to help class teachers identify and respond to youth in distress, closed identified gaps. Results indicated improvements in class teachers’ knowledge and attitudes towards self-harm and BPD. The intervention also improved the capacity of schools to plan and implement strategies to reduce the impact of mental health problems on the young person and their peers. A stay-at-school psychological care approach was fostered by enhancing partnerships between class teachers and school counsellors.