Increased calls for student, teacher, and school “accountability” have placed a greater emphasis on the need to assess what students know. While the focus of the calls for accountability is often on high-stakes testing, there are other important forms and purposes of assessment that deserve attention. In Principles and Standards for School Mathematics, the National Council of Teachers of Mathematics (2000) asserts, “Assessment should be more than merely a test at the end of instruction to see how students perform under special conditions; rather, it should be an integral part of instruction that informs and guides teachers as they make instructional decisions. Assessment should not merely be done to students; rather, it should also be done for students, to guide and enhance their learning” (p. 22).