But you can tell a lot about a teacher by how they respond when students don’t succeed. Some will say, “What’s wrong with you?” Others will ask, “What’s wrong with me?” great teachers know three things: they know their subject, they know how to explain their subject, and they know their students. Knowing the history of a topic, the interesting problems, the common misconceptions, the multiple approaches, the links to other topics. And it’s about expert communication of all of that. They co-create educational experiences with their students because they realize that students hold key knowledge of their own that most don’t acknowledge or even recognize.