Jena, about 220 miles north of New Orleans, is a small town of 3,000 people, 85 per cent of whom are white. Tomorrow it will be the focus for a race trial which could put it on the map alongside the bad old names of the Mississippi Burning Sixties such as Selma or Montgomery, Alabama.

Jena is gaining national notoriety as an example of the new 'stealth' racism, showing how lightly sleep the demons of racial prejudice in America's Deep South, even in the year that a black man, Barak Obama, is a serious candidate for the White House.

It began in Jena's high school last August when Kenneth Purvis asked the headteacher if black students could break with a long-held tradition and join the whites who sit under the tree in the school courtyard during breaks. The boy was told that he and his friends could sit where they liked.

The following morning white students had hung three nooses there. 'Bad taste, silly, but just a prank,' was the response of most of Jena's whites.

'To us those nooses meant the KKK [Ku Klux Klan], they meant, "Niggers, we're going to kill you, we're going to hang you till you die,"' says Caseptla Bailey, a black community leader and mother of one of the accused. The three white perpetrators of what was seen as a race hate crime were given 'in-school' suspensions (sent to another school for a few days before returning).

Jena's major industry is growing and marketing junk pine. Walk down the usually deserted main street and you will not find many black employees. Bailey, 56, is a former air force officer and holder of a business management degree. 'I couldn't even get a job in Jena as a bank teller,' she said. 'Look at the banks and the best white-collar jobs and you'll see only white and red necks in those collars.'

Billy Doughty, the local barber, has never cut black men's hair. 'They just don't come here,' he mumbled. 'Anyway, their hair is different and difficult to cut.'

The majority of blacks live in an area known as Ward 10. Many homes are trailers, or wooden shacks. Rubbish lies in the streets. On 'Snob Hill', where the whites live, the spacious gardens and lawns are trimmed, the gravelled drives boast SUVs and nice new saloons. Only two black families live there. A teacher from Jena High had enough money to buy his way in. But when he arrived local estate agents refused to show him a 'white' property even though several were advertised in the local paper ('they're all under contract,' the agents lied). The teacher eventually went to see one white owner and offered him cash. 'The guy preferred green [dollars] to black, so I got the property,' laughed the teacher, 'but since we moved in three years ago we haven't been invited by a single neighbour.'

On 30 November, someone tried to burn Jena High to the ground. The crime remains unsolved. That same weekend race fights between teenagers broke out downtown, and on 4 December racial tension boiled over once more in the school. A white student, Justin Barker, was attacked, allegedly by six black students.

The expected charges of assault and battery were not laid, and the six were charged with attempted second-degree murder and conspiracy to commit second-degree murder. They now face a lifetime in jail.

Barker spent the evening of the assault at the local Baptist church, where he was seen by friends to be 'his usual smiling self'.

Nine days later, with the case technically sub judice, the District Attorney made the following public statement to the local paper: 'I will not tolerate this type of behaviour. To those who act in this manner I tell you that you will be prosecuted to the fullest extent of the law and with the harshest crimes that the facts justify. When you are convicted I will seek the maximum penalty allowed by law. I will see to it that you never again menace the students at any school in this parish.'

Bail for the impoverished students was set absurdly high, and most have been held in custody. The town's mind seems to be made up.

But now the National Association for the Advancement of Colored People and the American Civil Liberties Union - 'damned outsiders' - have become involved and have begun to recruit, enthuse and empower the local black population. Reporters from the BBC and the New York Times have been drawn to the story. Jena does not like this publicity and shifts uncomfortably in the glare. It is 42 years since President Lyndon Johnson closed the loopholes that allowed southern states to discriminate against blacks. When the accused shuffle into court tomorrow, it's Jena that will be on trial.

· Tom Mangold reports 'Race Hate In Louisiana' for 'This World', BBC2, Thursday, 7pm.