In 1986, the Indianapolis and Gwinnett County (Georgia) school districts sat side by side on the list of the 100 largest school districts, each with slightly less than 51,000 students. But the districts were headed in opposite directions. By 2005, enrollment in Indianapolis declined by about 25 percent to 38,142, falling from the 63rd-largest to the 135th-largest district. Over the same years, Gwinnett County's enrollment grew by 184 percent to 144,598, rising from the 62nd-largest to the 15th-largest district in the nation. That is an extreme example of the enrollment trends reflected in this year's "American School & University" ("AS&U") 100--a compilation of the nation's 100 largest school systems. Suburban districts, especially in growing states such as Florida, Texas, California and Georgia, have experienced growth over the last two decades, while many urban districts have seen enrollments decline as the baby boom echo subsides and families seek alternatives to traditional public schools. This article describes enrollment trends on the "AS&U" 100 from 1986 to 2005.