The broad, contested notion of vulnerability is one of the areas of education in which concerns with the mental health and wellbeing of young people come together. This paper examines the theoretical and socio-political development of the 'vulnerability Zeitgeist' in recent years and the extent to which it has been applied to both young people and teachers in schools. We outline how the instrumental and negative views of vulnerability, which dominate policy discourse, run counter to the more expansive and ambivalent understandings familiar from sociological and psychoanalytic theory and use two cases drawn from studies undertaken in England and Germany to highlight their deleterious effects. Our analysis suggests that a more relational and collaborative approach, which explores vulnerability from the perspectives of both teachers and students, is necessary to improve support for the most vulnerable young people. We suggest that there are benefits to focusing on the vulnerability of young people and teachers, which research has until now examined separately, together conceptually and in practice to help to build trust and change attitudes to mental health and wellbeing in schools.