Interactions in the mathematics classroom affect both the mathematical learning and the identities of those involved. In this paper, we draw upon Discursive Psychology to examine how identities can be developed and altered in whole class interactions. In this sense, identity is not an attribute of a person but is something that is co-constructed through and in interaction. We demonstrate how these identities can shift moment-to-moment within an interaction. Importantly, these identities shift within the same interaction. These changes in identity development have important consequences for mathematical learning and continuing participation and contribute to our understanding of the variance in identities that students self-report.