HEAT, an instructional program emphasizing a nontraditional hands-on approach to algebraic instruction for urban, predominantly African American middle schoolers, provides a space to explore teachers' beliefs about urban students' mathematical abilities and motivation and addresses how teacher perceptions can intersect with instruction, learning, and the construction of students' mathematical identities. Using a multiple case study design, we analyzed six urban middle school mathematics teachers' written reflections and interview responses. Findings suggest that teachers' instructional behaviors, along with their perceptions and expectations of urban, African American middle schoolers' mathematical abilities and motivation, interact with students' beliefs and work habits in ways that can promote and support students' positive mathematical identity construction. Thus, HEAT personified thriving learning subcultures and supportive mathematical communities of practice that are far too atypical in urban middle schools.