“One problem with the systems of assessment that use letters and grades is that they are usually light on description and heavy on comparison. Students are sometimes given grades without really knowing what they mean, and teachers sometimes give grades without being completely sure why. A second problem is that a single letter or number cannot convey the complexities of the process that it is meant to summarize. And some outcomes cannot be adequately expressed in this way at all. As the noted educator Elliot Eisner once put it, “Not everything important is measurable and not everything measurable is important.”