From the perspective of deliberative democracy, the normative appeal of classroom discussions hinges on the deliberative quality of the discussion process. To better understand in which circumstances discussion might approximate the ideals of deliberation, the present study investigated the deliberative quality of classroom discussion in three conditions: a factual issue condition, a controversial issue condition, and a scaffolded controversial issue condition. Video observations from a classroom intervention were used to assess how each condition affected the deliberative quality of discussion. To this end, 202 student utterances were identified and coded by use of the Stromer-Galley manual for measuring aspects of deliberation. Though the scaffolded controversial issue condition produced more argumentation, contestation, and engagement than the factual issue condition, the controversial issue conditions also opened the door to more inequality, exclusion, and chitchat. Further research is needed on how teachers can tackle these issues, when they ask their students to engage in the democratic practice of discussing controversial issues.