Internationally there have been calls for the creation of sustainable learning environments. Education is seen as a key tool for building a sustainable community and society. A key issue in these debates is that the school curriculum should involve learners in a critical engagement on issues of social justice, human rights and social change by transforming attitudes and behaviours. This article presents a study that explored how discourses of social justice are created and generated in a classroom, and how they influence a teacher’s practices. The study involved one teacher at an urban secondary school in KwaZulu-Natal. Data generation tools used were interviews and lesson observation. Data analysis entailed the use of Critical Discourse Analysis (CDA). Three discourses of social justice embedded in the teacher’s assumptions and pedagogical practices emerged from the analysis: the discourse of academic excellence; the discourse of inclusivity and diversity; and the discourse of critical thinking. The study highlighted the need for further research into ways of supporting teachers in adopting a social justice approach to teaching and in creating empowering learning environments.