Summary: “Reasoning and sense making should occur in every classroom every day," states “Focus in high school mathematics: reasoning and sense making" [Reston, VA: NCTM (2009)]. As this book suggests, reasoning can take many forms, including explorations and conjectures as well as explanations and justifications of student thinking. Sense making, on the other hand, is “developing understanding of a situation, context, or concept by connecting it with existing knowledge" [loc. cit.]. Classroom assessment can provide opportunities for students to share and enhance their mathematical reasoning and sense making, allowing student reasoning and sense making to become visible to students and teachers so that they can respond in appropriate ways. However, what does such assessment actually look like in classrooms? This article draws on a multiyear research project of grades 7‒10 mathematics teachers to describe assessment practices that support students’ mathematical reasoning and sense making. (ERIC)