In Dynamic Teaching for Deeper Reading: Shifting to a Problem-Based Approach, the new book by Vicki Vinton, she writes:
"Feedback has long been seen as a powerful form of teaching, though increasingly researchers are recognizing that certain types of feedback are more effective than others. It turns out, for instance, that grades and written comments on student assignments, which are the most common type of feedback, are the least effective. That's because, as Dylan Wiliam writes in Embedded Formative Assessment, " in such situations, feedback is rather like the scene in the rearview mirror rather than through the windshield. Or as Douglad Reeves once memorably observed, it's like the difference between having a medical [checkup] and a postmortem.""