“History teacher Bob Alston's "expertise late not in his sweeping knowledge of the topic but in his ability to pick after a tumble, to get a fix on what he does not know, and to generate a roadmap to guide his new learning. He was an expert at cultivating puzzlement it was Alston's ability to stand back from first impressions, to question his quick leaps of mind, to keep track of his questions that together pointed him in the direction of new learning.”