Every year, in one out of three big cities, the school superintendent leaves his or her job, sending local community leaders back to square one. Cleveland, Baltimore and Washington, DC, are struggling to recreate their failed school systems and many more cities are likely to follow. City leaders need more than new superintendents. They need stable reform strategies strong enough to move an entrenched system. Unfortunately, it is not clear where they can turn for help. Education experts are deeply divided about whether teacher retraining or new standards are enough to reform a struggling city...