The US Supreme Court is about to rule on a controversy it had hoped to settle five decades ago - the issue of race in education.
Foes of desegregation plans resent 'bussing' of students
In the coming days, the justices are expected to decide on challenges to two programmes designed to ensure racial diversity in schools.
The cases - in Seattle and Louisville, Kentucky - reflect the fact that despite previous efforts by courts, many black and white schoolchildren in the US live and learn in different worlds.
The Supreme Court first outlawed school segregation in the landmark 1954 ruling Brown v Board of Education.
But as the white middle-classes fled to the suburbs, leaving black-dominated inner cities, local schools on each side remained largely immune to integration.
As a result, in the 1970s and 1980s, courts ordered some local authorities to set up "bussing" plans - ferrying children to distant public schools to ensure racial balance.
The Supreme Court has issued guidelines for these. But in schools that have never been - or are no longer - subject to court desegregation orders, school boards have in recent years set up their own schemes.
It is these programmes, put in place by elected bodies rather than judicial fiat, that the Supreme Court is now considering.
In Louisville, the school board requires that 15-50% of students in each public school should be African Americans.
Since some parts of the city are almost entirely black and others overwhelmingly white, this means bussing some children to other areas.
"Without the plan, kids, especially at Kindergarten or primary level, would go to school with members of their own race," Frank Mellen, a lawyer for the school board, told the BBC News website.
Louisville's schools were strictly segregated when Muhammad Ali was brought up there
Racial diversity in schools, Mr Mellen says, is a vital tool in overcoming divisions produced by segregated neighbourhoods.
"The plan produces a better understanding across that divide," he adds. "It better prepares students for life and work in an integrated society."
But some resent having their young children taken across town for the sake of racial diversity.
Crystal Meredith, the parent who launched the challenge, wrote in her brief that the plan "denigrates a five-year-old's self-worth" by colour-coding him.
Most opponents of the Louisville programme are white, like Ms Meredith. But some black people agree.
"African Americans are being unfairly treated," says Deborah Stallworth, a nurse who fought a decision to send her son to an elementary school across town. "We are not being given a choice."
She agrees that the school in her area was far from outstanding - but at least it was local.
"I prefer to have my kid go to a school for poor black people across the street rather than spend hours on a bus to go to a school for poor white people on the other side of town."
Mr Mellen says the programme is flexible, and the vast majority of students end up in the school of their choice.
"Officials work hard to help parents," Mr Mellen contends. "Only a minority are unhappy and they usually get a transfer to a school of their choice."
This, in fact, is what happened to Ms Stallworth's child, who eventually got a place in a school near her home.
She says this happened only because she made herself a nuisance and few black parents dare to pester officials the way she did.
In Seattle, a group of parents is similarly fighting a plan to use race as one of several factors for admission to some oversubscribed schools, insuring that the racial mix remains in line with the district average.
"It's offensive to the constitution to be saying there should be X percentage of whites or non-whites or Hispanics," says Harry Korell, a lawyer representing parents.
The two cases being considered by the Supreme Court will have implications for hundreds of US school districts that have adopted race-conscious programmes.
Racial integration was the focus of a bitter struggle in the 1950s
"This will decide whether local communities will be able to bring together children across racial lines," says Anurima Bhargava of the NAACP Legal Defense Fund - a group that supports the school boards in both cases.
Such voluntary moves, Ms Bhargava says, are particularly important in places like Louisville that are trying to overcome a bitter history of racial segregation and inequality.
For those seeking to use an increasingly conservative Supreme Court to defeat race-conscious measures, the stakes are equally high.
"The cases are enormously important," says Abigail Thernstrom, an academic and prominent proponent of colour-blind policies.
"The larger question on the table is - do we want to judge individuals by the colour of their skin or the content of their character?"