Others have been even more exhaustive: Magdalene Lampert, a longtime trainer of teachers, wrote a dense and detailed 500-page book that documents a single year inside a classroom. The most ambitious of these efforts bring to mind the Jorge Luis Borges short story “On Exactitude In Science,” in which cartographers try to design maps so precise that they describe the terrain down to the most infinitesimal point.

Green takes a more nuanced approach, emphasizing that there is no single magic method that can transform any teacher. Instead, she argues for the teachability of teaching with a host of case studies, research findings, and cross-cultural comparisons. Her conclusions are persuasive, but only to a point. A huge gulf still separates competence from excellence. Can we expect that even the best training will transform a significant number of teachers into the pedagogical equivalents of Kobe Bryant?

It's a worthwhile question, especially since a comparison between teachers and pro athletes runs throughout Green's book. Athletes analyze game film to study what worked in different situations and apply that knowledge when similar circumstances arise in the future. Green tells stories about teachers in Japan who engage in frequent and intense scrutiny of their own practices, arguing convincingly that structured weekly study of filmed lessons would benefit American teachers tremendously.

Some teachers, however, will learn more deeply and effectively than others. They will be better able to anticipate potential sources of students' confusion, to admit and correct their own shortcomings and mistakes, to adapt efficiently to the ever-changing flux of a dynamic classroom.

To return to the sports analogy, an NBA shooting guard can improve by analyzing other athletes. But when it's game time, he'll find himself facing a range of questions: Should he pull up for the perimeter jumper, drive inside to the hoop, drive inside and feed the ball back out to a teammate, or look for a post player in a strong position? The answer will always depend on the strengths of the particular player and his defender, as well as how much time remains in the game and many other factors. In other words, a particular approach tends to work well in a given situation—except when it doesn’t.

This is not because great teaching is some intangible gift, but because—like other intricate and demanding skills, from performing surgery to playing chamber music—it requires a mixture of tenacity and instinct. Does it make sense to interrupt a student whose reply is leading the class away from the relevant point? It depends on the student, the mood in the room, the teacher's personal style, the broader curriculum, and countless other factors.

Some teachers certainly realize this. Others, however, indiscriminately apply methods approved by pedagogical research. One of the least effective teachers I ever encountered had read somewhere that the best way to engage students’ attention was by moving around the room and broadcasting her own love for the subject. Both were potentially good ideas, but she applied them so zealously that many students found her constant motion distracting and her over-the-top enthusiasm bizarre.