*students’* mathematical arguments as they play out *in practice*. In this article, we share a tool developed to elicit teachers’ pre- and postevaluations of students’ mathematical arguments on a problem-solving task. We discuss the design of the tool and provide evidence of its utility. Our findings indicate that the tool can be used to (a) identify changes in teachers’ evaluations of student mathematical arguments over time and (b) inform the design of professional learning experiences.

^{*}**Megan Staples**, Associate Professor of Mathematics Education, University of Connecticut, Neag School of Education, 249 Glenbrook Rd – Unit 3033, Storrs, CT 06269, megan.staples@uconn.edu

**Jillian Cavanna**, Assistant Professor, Elementary Education – STEM & Innovation, University of Hartford, 200 Bloomfield Ave, Hillyer 324, West Hartford, CT 06117, cavanna@hartford.edu