<p>This study examined how a middle school mathematics teacher implemented formative assessment lessons and how the classroom gradually transformed into an environment that encourages students' participation in mathematical discourse practices. Data were collected through year-long observations of a seventh-grade mathematics classroom and interviews. Using a discourse practice framework, the study analyzed the verbal interactions between the teacher and students. The findings draw a picture of the evolving dynamics of mathematical discourse, where students increasingly mirrored the teacher’s talk patterns and engaged in mathematical practices. The data suggest that while the teacher made efforts to develop discourse practices, the class exhibited varying levels of mathematical discourse, with more engagement in discourse occurring during closing sessions compared to opening sessions. These findings highlight the teacher’s important role in shaping students’ collective mathematical communication and the importance of strategically implementing discussions throughout different phases of a lesson to support students’ mathematical reasoning and cultivate discourse practices within the classroom community.</p>