On Sept. 8, 1992, the first charter school opened, in St. Paul, Minn. Twenty-five years later, some 7,000 of these schools serve about three million students around the U.S. Their growth has become controversial among those wedded to the status quo, but charters undeniably are effective, especially in urban areas. After four years in a charter, urban students learn about 50% more a year than demographically similar students in traditional public schools, according to a 2015 report from Stanford’s Center for Research on Education…
