How can we assess accurately and fairly what students have learned? This is a question with which every teacher wrestles. But when understanding is the purpose of instruction, the process of assessment is more than just evaluation: it is a substantive contribution to learning. Assessment that fosters understanding (rather than simply evaluating it) has to be more than an end-of-the-unit test. It needs to inform students and teachers about both what students currently understand and how to proceed with subsequent teaching and learning.

This kind of assessment occurs frequently in many situations outside of school. Imagine a basketball coach working with his team during a practice session. He might begin by asking the team to concentrate on a few particular skills or plays. As the players scrimmage, he studies their moves, measuring them against his standards of skillful basketball playing. He usually pays particular attention to the strategies and skills he asked the players to concentrate on at the start of practice. He analyzes the problems when the team falls short and, as the team plays, tells them how they can improve their performance. Occasionally, he stops the practice session to bring the team together to provide more sustained feedback and to give the players new tasks, based on his assessment of their performance.

This kind of coaching continues through actual games. Games conclude not only with a score that tells the team how well it performed, but also with debriefing sessions in the locker room in which the coach and the team hash out what went well and what they need to work on before the next game.

Or think of a director's work as she rehearses a troupe of actors for a stage production. Each rehearsal is a continuous cycle of performance and feedback as the actors work through their scenes. The director gives initial instructions, offers advice and further direction while the scene is in progress, and convenes more formal feedback sessions at various points during the rehearsal.