In recent years, research on students' scientific argumentation has progressed to a recognition of nascent resources: Students can and do argue when they experience the need and possibility of persuading others who may hold competing views. Our purpose in this article is to contribute to this progress by applying the perspective of framing to the question of when and how a class forms and maintains a sense of their activity as argumentative. In particular, we examine three snippets from a sixth-grade class with respect to how the students--and the teacher--experience, or "frame", what is taking place. We argue that they show dynamics of framing for individuals and for the class as a whole that affect and are affected by students' engagement in argumentation. We close the article with implications of this perspective for research, teaching, and instructional design. (Contains 7 tables and 1 figure.)