This study analyzed segregation among public elementary school children using data collected by the National Center for Educational Statistics through the 1999-00 school year. It examined the impact of such factors as families opting out of the public school system or taking school attendance lines into account when deciding where to live, noting whether they combined to affect disparities in the racial and ethnic composition of schools. Overall, results indicated that separate meant unequal in U.S. public schools. During the study period, the average poor student attended a school that was 63 percent poor, while the average nonpoor student attended a school that was only 27.5 percent poor. White students were in schools that were 30 percent poor, black students were in schools that were 65 percent poor, Hispanic students were in schools that were 66 percent poor, and Asian students were in schools that were 42 percent poor. These disparities varied by region. This suggests that racial segregation works to the benefit of white students, placing them in very different schools from minority students. (Contains 10 tables.) (SM)