This article draws on critical theories and perspectives on mathematics education to explain the tendency of mathematics teaching worldwide to remain focused on developing procedural understanding, despite repeated calls from the mathematics education community for a more relevant and engaging curriculum. It highlights how conventional approaches to teaching mathematics contribute towards alienating a high proportion of learners and reproducing inequities within society. The article reports on a participatory action research project, involving a group of mathematics teachers in secondary schools in England, who share a commitment for teaching mathematics for social justice. It demonstrates how, by reflecting critically on their own epistemologies and classroom practice in relation to an underlying theoretical framework, teacher researchers are able to negotiate the constraints they face in achieving this objective. Careful consideration of their relationships with students enables them to develop pedagogies that significantly heighten the engagement, and advance the empowerment, of students.