Amanda Ripley tries to answer the question in the current Atlantic. A sizable excerpt:
Great teachers tended to set big goals for their students. They were also perpetually looking for ways to improve their effectiveness. For example, when Farr called up teachers who were making remarkable gains and asked to visit their classrooms, he noticed he’d get a similar response from all of them: “They’d say, You’re welcome to come, but I have to warn youI am in the middle of just blowing up my classroom structure and changing my reading workshop because I think it’s not working as well as it could.’ When you hear that over and over, and you don’t hear that from other teachers, you start to form a hypothesis.” Great teachers, he concluded, constantly reevaluate what they are doing.
Superstar teachers had four other tendencies in common: they avidly recruited students and their families into the process; they maintained focus, ensuring that everything they did contributed to student learning; they planned exhaustively and purposefullyfor the next day or the year aheadby working backward from the desired outcome; and they worked relentlessly, refusing to surrender to the combined menaces of poverty, bureaucracy, and budgetary shortfalls.
But when Farr took his findings to teachers, they wanted more. “They’d say, Yeah, yeah. Give me the concrete actions. What does this mean for a lesson plan?’” So Farr and his colleagues made lists of specific teacher actions that fell under the high-level principles they had identified. For example, one way that great teachers ensure that kids are learning is to frequently check for understanding: Are the kidsall of the kidsfollowing what you are saying? Asking “Does anyone have any questions?” does not work, and it’s a classic rookie mistake.
(Video hat tip: TED)