Dan Willingham, a professor of psychology at the University of Virginia, is a leading expert on how students learn. “Data from the last thirty years leads to a conclusion that is not scientifically challengeable: thinking well requires knowing facts, and that’s true not only because you need something to think about,” Willingham has written. “The very processes that teachers care about most — critical thinking processes such as reasoning and problem solving — are intimately intertwined with factual knowledge that is stored in long-term memory (not just found...