This paper summarizes variations in instructors’ implementation practices during Peer Instruction (PI) and shows how these differences in practices shape different norms of classroom interaction. We describe variations in classroom norms along three dimensions of classroom culture that are integral to Peer Instruction, emphasis on: (1) faculty-student collaboration, (2) student-student collaboration, and (3) sense-making vs answer-making. Based on interpretations by an observing researcher, we place three different PI classrooms along a continuum representing a set of possible norms. We then check these interpretations against students’ perceptions of these environments from surveys collected at the end of the term. We find significant correspondence between the researchers’ interpretations and students’ perceptions of Peer Instruction in these environments. We find that variation in faculty practices can set up what students perceive as discernibly different norms. For interested instructors, concrete classroom practices are described that appear to encourage or discourage these norms.