In this study, the author examines the ways a small group of students and their teacher from an intermediate-level university writing class use the texts they create to negotiate private and shared public understandings of the complex interactional contexts of their work together. The author begins by examining some of the competing goals and motives that energize the participants' classroom efforts. To understand the sources of those diverse purposes and how they serve to shape and sustain subsequent classroom interactions, the author develops an activity-based framework of analysis that draws extensively from dialogical and functional-linguistic approaches to language, context, and interaction. Writing and written communication are portrayed as linguistically mediated and interactively structured processes of contextualization. Implications for how we conceptualize and organize classroom interactions, such as intensive peer review and student-teacher conferencing, and the central role that talk and writing must play in operationalizing those interactional contexts are discussed.