This study addresses the complex challenges of childhood obesity, food poverty and environmental degradation by developing a planetary health framework for school food in education. Drawing on Dewey's experiential learning philosophy, it adopts an integrative approach where school meals and food education converge. Rooted in the planetary health model, the research explores the interdependence of human and environmental health within the context of school food. Employing a convergent mixed-methods approach, we conduct interviews, a web-based survey and observations in English primary schools to explore multiple stakeholders' perspectives on sustainable school food. Findings underscore three defining characteristics of sustainable school food: reversion to scratch cooking, prioritising local and agroecological food procurement and promoting plant-based meals. Findings stress the convergence of health and environmental sustainability within school food, highlighting the need for a planetary health approach to school food where meals and education are integrated into school food experiences. Experiential food education, such as cooking and farm visits, supports sustainable school meals provision and their use as a pedagogical tool, embedding sustainable food practices into pupils' everyday school experiences. The study underscores the role of ethical leadership in allocating scarce resources and empowering often marginalised stakeholders such as catering staff and local producers to mobilise school food partnerships. Such partnerships generate mutual benefits, such as supporting local agroecological food production and challenging the dominance of processed foods in school menus from large corporations.