Although discussion has long played a role in classroom learning, recent focus on moving discussion away from the evaluative and toward the dialogic is key to understanding how discussion can be driven by multiple, shared understandings. Adopting a sociocultural perspective, this dissertation explores the ways in which identity performances shape one teacher and his students' participation in classroom discussions. The theoretical framework guiding this study draws on the relationship between discourse and identities construction, with further attention given to improvisations of identities, figured worlds, and the ways in which power shapes discourse. This dissertation argues that performed identities shape the ways in which discussion participants engaged in critical talk, particularly in how participants develop disagreement, engage in perspective taking, and foster power, agency, and voice in the classroom. Ultimately, this study suggests that it is imperative to consider the ways in which teachers navigate disagreement in the classroom, provide opportunities for students to participate in political discussion, and consider the ways in which participants' identities may shape discussion. vii