The dramatic shift in the demographic makeup of Roanoke's schoolchildren both reflects changes in the city's total population and offers a glimpse of the city's future.

Part of the explanation lies in an old phenomenon: white flight from urban centers like Roanoke, said demographer Julie Martin, who recently retired from the Weldon Cooper Center for Public Service in Charlottesville.

Just as in the school population, the percentage of whites in Roanoke decreased from 1990 to 2000, according to the U.S. Census Bureau. The number of white school-age children fell by 1,510. But at the same time, the number of blacks that age increased by 814.

Even that doesn't account for all of the change in the schools. It's not as simple as white families moving to Roanoke County, for example.

The county gained about 700 students from 1995 to 2004, but only 100 were white compared with 300 who were black. Two hundred were Asian.

Roanoke has long been the hub for the region's poor, largely because of the concentration of services and low-income housing in the city. Blacks continue to be disproportionately more poor than whites. In 1999, nearly 27 percent of blacks were below the poverty line, compared with about 11 percent of whites.

But while the city population of 93,600 is just over one-quarter black, nearly half the school population is.

Martin and urban demographer Dowell Myers of the University of Southern California say that's because the general population shifts are exaggerated among school-age kids because of several factors.

The black birthrate nationally and locally has long outpaced the white birthrate.

Private schools tend to siphon off white and well-to-do students, too. While the percentage of Roanoke students in private schools is half that of the nation, that number grew from 655 students in 1990 to 904 in 2000, the census shows. In 2000, 84 percent of Roanoke students in private school were white.

In addition, every year a few hundred students who live in the city attend Roanoke County or Salem schools -- 150 in Salem alone, those school divisions report. Most are the children of school system employees in those localities.

Furthermore, 140 city students on average are home schooled each year, according to the state Department of Education.

Still, Martin and Myers agree, the demographic profile of today's students is a window to the future of Roanoke's population.

"Unless a growing number of young white adults are moving into the city to stay," said Myers, "in 10 years ... the pattern you see at age 5 or 15 will prevail at 15 and 25."

Staff writer Ray Reed contributed to this report.