Public school segregation in the United States has changed substantially over the past quarter century. The fraction of minority-segregated schools has roughly doubled, but the share of whitesegregated schools has decreased at an even faster rate. As a result, the prevalence of segregated schools has decreased in most parts of the country. Using data on the universe of US public school enrollments, we develop an empirical approach that allows us to decompose observed changes in segregation into three exhaustive channels: active (discriminatory) sorting, passive (non-discriminatory) sorting and aggregate demographic change. Although segregation and discrimination have often been treated as synonymous, we find that the discriminatory channel has been the least important of the three in explaining recent trends. Instead, demographic change, largely due to Hispanic immigration, is the most important channel. These findings are particularly pronounced in the largest urban areas in the country, which not only experience the largest changes in segregation during this period but are also the areas in which policymakers are most concerned about the pernicious effects of segregation.