What is the role of schools, and more specifically school leadership, in the transition to a sustainable future for humankind? What different forms of leadership are needed to enable this role? The challenges are huge and complex and for those of us engaged in promoting sustainability learning, it is clear that the issue has never been more pressing. Action at government and corporate level is required, as well as an immense shift in patterns of consumption, especially in richer countries. This paper aims to explore the nature, challenges and opportunities of sustainability leadership within the context of formal education in the UK. A critical pedagogy (Freire, 1970; Gatto, 1992) lens is used to explore ways in which the formal education system is constructed on mental models that are inherently unsustainable, and that reinforce the principles of hierarchy, power and control, separation, competition and colonialism that are at the root of sustainability challenges. Drawing on interviews with school leaders, some possibilities will be explored, such as alternative pedagogies that create space for relaxed, collaborative, co-constructive learning, that encourage critical thinking, and reignite children's sense of connection with each other and with the environment (Woodlin, 2014).