And the lesson today is how to shoot

When Class Enemy premiered in Sarajevo last year, it faced complaints from an angry audience who said it exaggerated the social problems of the Bosnian capital. "They accused us of overacting," says Amar Selimovic, who plays Iron in Nigel Williams' searing 1978 play, relocated to Bosnia in a bold new adaptation. "They said, 'We don't have those sorts of problems here.' We said, 'Maybe you should take a closer look.'"

While they were rehearsing Klasni Neprijatelj, as it is in translation, the actors of the East West Theatre Company followed crime reports in the papers. These stories, referred to in Bosnia as "black chronicles", focused on violence in schools, which involved knives, guns and even bombs. Most shocking was the attack last February on a schoolboy travelling home by tram, stabbed to death by three pupils. The attack prompted 20,000 Sarajevans to take to the streets in protest at the growing violence in schools.

EWTC actors conducted their own research in the colleges and schools of Sarajevo. They found a frustrated generation of children from broken homes, whose parents were still suffering the devastating effects - psychological and material - of the 1992-95 war. Just like the characters in Williams' play, they were desperately searching for direction, but were thwarted by their circumstances. "I spent time in a butchers' school," says Selimovic, 26. "The kids spent their time chucking meat at each other. They told me when they qualified, they wanted to become criminals, because it was a more interesting life: the cars, the girls. I was shocked."

Director Haris Pasovic took Williams' play, set in 1970s Brixton, and thrust it into contemporary Sarajevo. Cast and crew are from across the national spectrum: Bosnian Muslims, Serbs, Croats, all with disturbing stories of the war. The play's themes of confused social values, isolation, single-parent families, alcoholism, xenophobia and violence were a strong fit, although Pasovic tweaked cultural references and dialogue to make it more accessible to a Bosnian audience.

The new version - which comes to Edinburgh later this month, performed in Bosnian with English supertitles - is just as shocking as the original. In one brutal scene, Cobra, a dangerous classroom beauty played by 24-year-old Maja Zeco, tells her head teacher: "I'll give you such a kicking, your mother will have to scrape you off the floor with a spatula." The words came straight from the mouth of a Sarajevan schoolgirl.

"We picked up the language in the classroom, in the playgrounds," says Pasovic, a jovial figure, sitting on a sofa in EWTC's headquarters, a rented flat in central Sarajevo. "The variety of expressions is mind-blowing, and the girls are no better than the boys." South London slang has been replaced with its modern Sarajevan equivalent - a vocabulary that, like the young people themselves, has been shaped by the war. "Horror has entered their vocabulary," Pasovic says. "I was 30 when the war started. Then I had no idea what 'mass grave' meant. But they've incorporated it into their language. It's part of their culture."

In a playground one day, he heard the line: "If I get hold of you, Amor Masovic won't be able to recognise you." Masovic was head of the forensics team responsible for finding mass graves and identifying their disfigured victims. "I decided to put it in the play," says Pasovic. "It just begins to scratch the surface of the Bosnian catastrophe."

The production has forced the issue of youth violence to the fore in Bosnia. At its premiere, Pasovic seated the president of Bosnia Herzogovina, of whom the play is critical, in the same row as a group of juvenile criminals who had never been to the theatre before. For Pasovic, it was a small victory in his battle to highlight a neglected generation now coming of age.

Williams' Class Enemy is set in a dilapidated classroom ("It's crap innit? There's no books, no chalk, no pencils, no windows - just us an' the bleedin' desks, innit?") where foul-mouthed students wait for teachers who never arrive. Instead, in a drama that borrows from the best of Waiting for Godot and Lord of the Flies, they barricade themselves against the outside world and conduct their own lessons, which grow ever more brutal and end in tragedy. Chairs are hurled, there is simulated rape, while the frenzied swearing illustrates how ill-equipped the characters are to express their true feelings.

EWTC are rehearsing in Sarajevo University's bombed-out engineering faculty. The building, spewing out cables and dangling debris, sits on the former frontline of the war. Emerging from an energy-fuelled rehearsal, in which a former Croatian soldier gave tips about how to handle guns, the sweaty cast use their mobile phones to light the way down the broken steps of the unlit building. Zeco, from Mostar, recalls the weeks on end she would spend in the cellar of the family home during the war, "praying the grenades would not hit our house".

Amar Selimovic, who comes from Tuzla and was 10 when the war started, says the play speaks for a whole generation of children: "Lots of families have someone whose bones were never found. I went to a psychologist to ask what I could do about my anxiety attacks - I see pictures in my head of the war, the bloody bodies. She said I would just have to live with it." He brought his mother, a secondary school teacher, to see the play. "My ma was shocked by the rudeness of it and said she couldn't feel her legs after. But what most shocked her was how close to her experience of the classroom it was."

ETWC, which was founded in 2005, is a pioneer of independent theatre, surviving precariously on ticket sales and public donations. Such difficulties are nothing compared to what Pasovic has previously endured. During the four-year siege - when Sarajevo was surrounded by Serb snipers who rained bullets and grenades on the city day and night, cutting off electricity and water supplies - Pasovic ensured that theatre continued, at one point working with Susan Sontag on a candlelit production of Waiting for Godot.

More recently, he brought the city's traffic to a halt, by staging a grand Romeo and Juliet in front of the bombed-out parliament building in 2002. On the walls of Pasovic's office are messages of support, faxed to him during the siege from, among others, Stephen Hawking and Carl Sagan - each one a reminder of the years when the city struggled to stay alive. "There's no real theatre," he says with a smile, "without taking risks" ·

· EWTC are in conversation with Nigel Williams at The Hub, Royal Mile, Edinburgh, on August 22 at 2.30pm.