High school chemistry teachers struggle to use assessment results to inform instruction. In the absence of expert assistance, teachers often look to their peers for guidance and support; however, little is known about the assessment beliefs and practices of high school chemistry teachers or the discourse mechanisms used as teachers support one another. Presented in this paper are the results from analyzing a discussion between five high school chemistry teachers as they generated a set of best practices for inquiry assessments. To analyze the discussion, a novel representation called a discourse map was generated to align the analyses conducted on chemistry teacher discourse as they temporally occurred. Results show the utility of the discourse map for evidencing critical friendship and assessment practices evoked by the teachers during the discussion of best practices. Implications for the structural considerations of materials and chemistry teacher professional development are presented as well as potential future investigations of teacher discourse regarding the use of data to inform instruction.