Teachers are key professionals in responding to children and adolescents with possible mental health difficulties and who exhibit social, emotional or behavioural difficulties in the classroom. Health and education policy increasingly positions teachers as vital agents in connecting mental health services with affected young people. A growing corpus of research, however, questions practitioners' capacity to undertake this important role, particularly given the limited space afforded to content around mental health in pre-service teacher education. This paper reports on a qualitative case study, conducted in an Australian context, investigating pre-service teacher responses to five vignettes of young people presenting behaviours indicative of possible mental health difficulties. In light of educator expectations to identify and appropriately respond to mental health difficulties, this study discloses the need for explicit, structured mental health guidance which form a discrete, core "knowledge base" of teacher education. Patterns in data, analysed in light of policy literature, also suggest the value inherent in advocating open-minded, non-judgemental and collegial professional responses. Further research opportunities highlighted include a systematic review of current provision around mental health in pre-service teacher education programmes.