Although it is true that most schools in the U.S. are either made up of mostly white or black students, this does not mean that racism is still a problem. Schools that are made up of mostly black students are in communities which black people were forced to live long ago. Despite the fact that segregation no longer limits black people to live in ghettos (and when I say "ghetto," I mean a community inhabited a single ethnic group, which is its true meaning), it was still hard for them to get the money move out of the ghetto and into a new home. As a result, these communities still consist of mostly black people and there are only black students in the schools for those areas.
The way I see it, there's really no way to fix this problem without forcing people to move out of their homes and into an entirely different community even if its against their will. That's not racism that's just how things are; although it could definately be said that all of this is a result of racism. But the fact still remains that there are simply less black people living in the U.S. than white people. So even if all schools had an equal amount of black and white students in every school in America, there would still be more white students.