Along with Tom Loveless, Robert Pondiscio and David Steiner, count me among those who are less than enchanted  by Elizabeth Green's new book. The journalist—who did such a fine job as a blogger about New York City education issues—has definitely written an engaging book. Unfortunately, it is in the service of a weak theory that may divert us from making the right changes in how teachers are trained.

In a nutshell, Green's argument is that two teacher educators, Deborah Lowenberg Ball and Magdalene Lampert (both very prominent in teacher ed circles), have perfected the student-centered, discussion-based instructional practices that parallel those in Japan's math classrooms. By contrast, Green argues that while the "teacher moves" developed by Doug Lemov (very prominent in the world of charter schools) bring order to often chaotic urban classrooms, they stifle student interaction and thought. (A more charitable portrayal, at least, than by those in teacher ed who view Lemov as promoting nothing more than a "bag of tricks.")

Nearly two decades into their work, neither Ball nor Lampert has yet to produce any research demonstrating that teachers who employ their methods produce greater learning gains than teachers who do not, a vacuum that may have passed muster years ago, but can't be tolerated any more. Ball has laid out an impressive research agenda into the relevant questions, but—to our knowledge—neither she nor anyone else has set about answering those questions. Nor, apparently, did Green demand that the heroines of her story show her the proof that their methods were effective, instead drawing parallels to Japan's classrooms.

Reviews to date of Green's book have also noted the lack of research evidence and the problems with drawing parallels between American and Japanese schooling. But they have missed another obvious weakness, which William Schmidt's studies about  the self-professed teaching difficulties of our elementary teachers and the middling preparation of our middle school teachers internationally make quite clear: many of our teachers have a difficult time teaching math at even a procedural level. Whatever the pedagogical value of probing, student-centered discussions of math concepts, ignoring the fact that Japanese teachers can orchestrate such discussions because they are better-versed in math ignores a critical factor in improving the preparation of U.S. teachers. What's missing from the Green story is a simple, matter-of-fact observation: teachers can't teach what they don't know. Any discussion of the pedagogy of math instruction that doesn't explicitly address the issue of content preparation is deficient on its face.