While access to secondary school is increasingly available to a larger and more heterogeneous population of learners, expansion in enrolment masks the reality that educational inequalities are widening. Using a comparative and in-depth qualitative research design, this dissertation explores processes of educational inclusion and exclusion as they unfold within the classroom walls, where it is teachers who determine how access to the curriculum and classroom culture is created and sustained. Data generated through 12 lesson observations and accompanying stimulated recall interviews enable consideration of how patterns of teacher discourse influence teacher capacity to foster inclusivity, and why such patterns emerge. Data gathered through key informant interviews and focus group discussions support the scrutinization and triangulation of tentative findings drawn from the observation and stimulated recall data. This research is premised on the need to expand our knowledge of what inclusive education can mean in classrooms typically characterized by material and human deprivation, and in teaching approaches most often defined by a strong pedagogic tradition of knowledge transmission. The findings support the construction of an explanatory framework revealing the ways in which patterns of classroom discourse shape teacher capacity to foster inclusion in Tanzanian secondary school classrooms. They reveal the importance of three moments embedded within each teacher-student interaction: The moment within which a turn is allocated, the moment within which a student response is interpreted by a teacher, and the moment within which a teacher then follows up. The findings demonstrate the power of the multiple continua of discursive strategies within which teachers move, revealing the specific decisions and respective trade-offs which influence teacher capacity to foster processes of educational inclusion. The findings are significant for expanding our understanding of the intersection between pedagogy and inclusion in the Tanzanian context, generating insight into that which teachers do, the reasons for why they do it, and the contextually relevant levers for change.