The survival of the school-reform movement, as it’s known to champions and detractors alike, is no longer assured. Even a couple years ago, few would have predicted this turn of events for a crusade that began with the publication of A Nation at Risk in 1983, gathered momentum as charter schools and Teach for America took off in the 1990s, and surged into the spotlight with No Child Left Behind in 2001. As a schoolteacher, I know I didn’t anticipate this altered landscape. If one person can be credited—or blamed—for the reform movement’s sudden vulnerability, it’s a fiercely articulate historian, now in her 70s, named Diane Ravitch.

That Ravitch helped conceive the movement she now condemns makes her current role even more unexpected. Almost four decades ago, Ravitch emerged as a preeminent chronicler of, as she put it, “the rise and fall of grand ideas” in American education. The author of 11 books, including Reign of Error (out this month), she has traced the past century’s successive battles over how best to deliver a quality education—and to whom.

In 1991, she shifted from observer to policy adviser, becoming an assistant secretary of education under George H. W. Bush. An outspoken critic of progressive pedagogical theories, she urged rigorous national standards and gravitated toward conservatives promoting parental choice, vouchers, and charter schools. Market-based alternatives, she decided, were the answer for impoverished parents desperate to see their children escape broken inner-city schools....