When the mayor and public school officials in the District of Columbia unveiled plans last month for converting Washington's middle and elementary schools to a pre-K-8 model, system leaders seemed confident the change would be good for students. After all, the school system has plenty of company. Since the late 1990s, districts in a growing number…

This article deals with school districts' K-8 configurations. Cincinnati, Cleveland, Milwaukee, New York, and Philadelphia are among the districts making the change, driven by a small body of research and a rising pile of anecdotes suggesting that K-8 configurations help academic performance, decrease discipline problems, enhance parent…