This article reports on a two-year qualitative, practitioner-research study of teaching and learning for social justice. The site was my middle-school mathematics classroom in a Chicago public school in a Latino/a community. A major pedagogical goal was to create conditions for students to develop agency, a sense of themselves as subjects in the world. My research suggests that students learned mathematics and began to develop sociopolitical awareness and see themselves as possible actors in society through using mathematics to understand social injustices. This research contributes to our understanding of how to create opportunities for students to develop agency in K-12 mathematics classrooms, and may also contribute to our knowledge of developing agency in any subject area.