America's largest civil rights group sued Nebraska law-makers last week to block the division of its largest education authority into three along racial lines.
Under legislation passed last month, Omaha's school system will be broken up into three education authorities - one covering largely black schools, another mostly white ones and a third predominantly Hispanic - in 2008.
About 45,000 pupils are affected.
Its architect, Ernie Chambers, the state's only black senator, said last week the law addressed the reality of postcode segregation, offering minorities greater educational control than under a unitary authority.
"It's an attempt (by) non-white people to govern... their own community,"
But the National Association for the Advancement of Colored People said that the move violated the constitutional ban on school segregation.
Tommie Wilson, president of the association's Omaha chapter, said: "Schools should be (places) where students have the opportunity to learn from and be exposed to others from diverse racial and ethnic backgrounds, not places of racial isolation that may very well lead to greater racial tension.
Segregation is a moral wrong, regardless of who advocates it."
No court dates have been set, an association spokeswoman said.