In this study, I use a systemic functional linguistics approach to examine mathematics classroom discourse with the aim of providing a plausible explanation of how students could actively participate in productive classroom discussions without adopting ways of reasoning that were accepted in the classroom community. In this way, I work in the crossroads of a research tradition examining classroom interaction and a research tradition that examines student learning. I found that even though particular ways of reasoning about exponentials and logarithms were advanced and accepted in the classroom discourse, the way these ways of reasoning were talked about in the class did not preclude students from maintaining less sophisticated ways of reasoning Specifically, I argue that the two exponential ways of reasoning were not explicitly contrasted, which may have contributed to students seeing them as essentially the same strategy. [For complete proceedings, see ED581294.]