Many teachers, pastoral care staff, counsellors, psychologists and others from related disciplines who support children and young people's (CYP's) personal, social and emotional development are concerned by declining well-being and the increased demand for pastoral care and counselling for students with social, emotional and mental health (SEMH) needs. For practitioners to meet these SEMH needs effectively requires both an understanding of them and, more importantly, how CYP "themselves" make meaning from them. Psychological theories, especially those applicable to exploring experiences that evoke strong emotions, are vital. This paper outlines one such theory-informed approach: a collaborative approach to SEMH assessment at times of school transition. Specifically, it examines a novel use of projective techniques (PTs), where CYP are asked to provide a free-flow response to a stimulus ["Content"] and then think together with the practitioner about this response ["Dialogue"]. Reflective accounts of the method are provided to outline how it can support CYP's engagement in assessment; enhancement of shared insights in formulation and personalisation of interventions. These are critical case study vignettes of using this new approach in applied practice, and there is a priority need for further empirical research. Other limitations and strengths of using PTs are outlined, and implications for future developments provided. Finally, an argument is made that system level transformation may be required if the necessary support for school-based staff to make effective use of these tools is to be realised.