Inclusion and detracking policies seek to remedy the pervasive inequality of educational opportunities in U.S. schools by building classrooms that are integrated across the lines of race/ethnicity, class, and disability and that offer all students access to a rich and challenging curriculum. In practice, however, teachers often struggle with the implementation of these reforms. Drawing on ethnographic research in detracked and inclusion classrooms, this article analyzes the nature and sources of the tensions and dilemmas felt by teachers working in intentionally heterogeneous settings. It argues that the implementation of these policies is not often accompanied by a serious interrogation of the taken-for-granted understandings of ability, standards, and structural inequality that pervade educational discourse inside schools. This failure to challenge dominant discourse about these three issues is at the root of the tensions and dilemmas felt by teachers working in detracked and inclusion classrooms. Drawing on lessons learned from research, the authors propose a capacity-oriented framework for teacher education that might better prepare teachers working in intentionally heterogeneous classrooms to meet the equity-minded goals of these reforms.