When Diane Ravitch decided that reform ideas like robust testing, charter schools, and No Child Left Behind were imperiling rather than saving American education, she managed to break with her former Republican allies and start a fight with Obama Democrats, all at once....

Teachers unions and some civil-rights groups sounded these alarms before Ravitch did. But her sharp writing and mastery of history (she’s an education professor and historian at New York University) mean that no one makes the case more forcefully....