This paper outlines current theories of teacher practice that seek to promote equity from critical perspectives, and contributes to the empirical research on critical mathematics equity practice. Part of a larger study of equity and mathematics teacher practice in an urban public school, this paper reports specifically on the involvement and practice of one experienced 8th grade teacher chosen for her experience as a community activist and her participation in the creation of the school. It reports on the considerations that went into the planning of the school and its mathematics program, and the tensions and difficulties this teacher faces as she seeks to make her practice more critical. Data include documents related to the school's creation, classroom observation notes, and an initial interview. These data indicate that the mathematics program structure and curriculum draw from existing data on equity practice, and were carefully considered to align with the school's dual goals of college preparation and preparation of students to work for social justice. The focal teacher's description of her existing practice reflects the critical pedagogy literature and the literature on implementing social justice curriculum in mathematics. The teacher provides examples of social justice mathematics projects she has implemented, and highlights tensions and difficulties she faces in that implementation. She articulates tension between the desire to implement critical mathematics projects and other the priorities she feels are most important for equity and social justice. At the same time, she exhibits a commitment to continued struggle for equitable change. This teacher's efforts demonstrates work toward mathematics equity from a critical perspective, built from the ground up and initiated by full-time secondary educators dedicated to school-wide efforts at equity, social justice, and social change. The tensions and difficulties articulated by this teacher-activist provide a picture of the complexities of such work, even in a favorable context. This teacher's experience raises questions about expectations of classroom teachers' developing curricula that are both mathematically rich and critical. As this study continues, it will provide a more detailed view of the tasks facing critical educators working toward mathematics education that contributes to reducing inequity. Appended is: Focal Teacher Preliminary Interview Codes, Spring 2007. (Contains 9 footnotes.)