The socio-political and educational context in which this current research is situated supports a neoliberal agenda and therefore contributes to the complex discourse around mental health (MH) in the UK. However, as MH has become a higher-profile priority for the UK government, over the last decade, initiatives have begun to focus on promoting mental health in educational contexts. As a result, schools have been recognised as having the potential to embed universal approaches for positive MH development. One such school-based MH initiative was announced in 2017 with the introduction of Youth Mental Health First Aid training (MHFA) for every secondary school in England. However, with the exception of an evaluative piece of research into the Youth MHFA programme, there is limited research into the views of secondary school practitioners’ interpretation of the term ‘mental health’ and perceived emotional availability to promote the MH of their students. Therefore, this study aimed to explore the ways in which a small group of Mental Health First Aiders and teachers working in mainstream schools constructed the term ‘mental health’. Data was gathered using semi-structured interviews and analysed using thematic analysis. Themes were explored and identified in relation to the practitioner’s understanding of the term ‘mental health’ and how available they feel, to promote their students’ mental health in school. Numerous themes were identified in relation to the practitioners’ conceptualisation of MH, and alongside referring to a biomedical model, there was reflection upon the complex interaction between psychological and social factors related to the development of MH difficulties. Further, the significance of the relationships between school staff and their students, parents and colleagues within the context of supporting CYP’s mental health emerged from the analysis. Findings also highlighted the ways in which school staff are available to promote their students’ MH, as well as the barriers which exist within this. For example, the impact of working in this field on school staffs’ wellbeing, which illustrates the importance of professional support, such as supervision, which it can be argued EPs are well placed to provide. In light of the current mental health challenges in the UK, the present study suggests that the introduction of specific interventions such as MHFA Champions need to be complemented by a wider whole-school systemic focus on MH and wellbeing which aims to connect CYP with their broader social and cultural worlds.