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Justification is a core mathematics practice. Although its role in the mathematician community has been studied extensively (e.g., Hanna, 2000), we know relatively little about its role in K-12 classrooms. This study was conducted to clarify aspects of justification as a learning practice in middle grades mathematics classrooms. We document the views of 12 middle grades teachers who were working actively to incorporate justification into their classrooms. We further analyze differences between teachers’ purposes and mathematician purposes, and how these differences may reflect the different purposes of the two communities. Implications for mathematics education and teacher development are discussed.


The preparation of this paper was supported by a grant from the National Science Foundation (NSF) (DRL-0814829). The views expressed are those of the authors and do not necessarily reflect the views of the NSF.

The paper was peer-reviewed and accepted for publication in the Proceedings of the thirty-second annual meeting of the North American Chapter of the International Group for the Psychology of Mathematics Education. The paper was withdrawn from publication, however, as the authors could not attend the meeting. A revised and extended version of this paper is being prepared for journal submission. Inquiries can be directed to Megan Staples (