Classroom assessments fall into three categories--summative, diagnostic, and formative. Summative assessment occurs at the end of a unit or course of study and is therefore an insufficient tool to maximize student learning. Diagnostic and formative assessments, on the other hand, offer descriptive feedback along the way. In light of these categories, authors McTighe and O'Connor consider several assessment and grading practices that can enhance teaching and learning. Teachers should use summative assessments to frame meaningful performance goals, show criteria and models in advance, assess before teaching, offer appropriate choices, provide feedback early and often, encourage self-assessment and goal setting, and allow new evidence of achievement to replace old evidence. (Contains 2 figures.)