Two boys are in the locker room, talking about sex. "Can you imagine?" one says. "You'd have to get naked in front of" - he spits the word out, his disgust palpable - "girls." "Yeah," his friend agrees. "Horrible."
The first boy wrinkles his brow. "I mean, it's possible to be gay and like football," he says, his tone a question mark. "I like cars and drinking beer in pint glasses. But I don't like girls."
In these boys' world, most people are lesbian or gay. Heterosexuals hide their preferences from others; "hetero" is considered a form of abuse. In the locker room where the boys sit, graffiti offers a mobile phone number beneath the words "John, the dirty snatch-bandit".
This is the version of reality envisioned by The Homophobia Project, a film designed to tackle homophobia in schools. The feature-length film has been released to coincide with February's Lesbian, Gay, Bisexual and Trans History Month.
It tells the story of Janet and John, heterosexuals in a world of uniform gayness. All children at Alan Turing High School have been conceived through artificial insemination, and brought up by same-sex couples.
Janet is eight when she discovers it is possible for a man and a woman to fancy each other. "Sir?" a classmate asks. "What's heterosexual?"
There is a pause, during which the teacher's benign paternalism transforms into unequivocal fury. "How dare you?" he rages. "You must never, ever ask me about anything like that."
Eight-year-old John, meanwhile, does not fit in: unlike most boys, he is not interested in reading magazines or gossiping. Instead, he likes football and the colour blue. His classmates pick up on his difference immediately: "Hetero! Hetero! Hetero!" they jeer, hands banging on the desks in front of them.
Life does not get better for him with age. While teenage Janet acquires a girlfriend and plays the part of "the perfect little lesbian", John suffers "het-boy" taunts on a regular basis. "If dirty little perverts like you start sleeping with all the girls," a bully spits at him, "there's not going to be enough to go around".
Eventually, he confides in Miss Gilbert, a sympathetic teacher. "Do your mums know?" she asks him. John shakes his head: "They have heterosexual friends and stuff," he says, "but they've always assumed I'm homosexual."
Miss Gilbert tells him that she, too, is straight. Soon afterwards, John is cornered by his English teacher. "It's come to light that you've had a conversation with Miss Gilbert," he says. "Did she act in any way inappropriately towards you? Did she make any advance, ask intimate questions, touch you?"
Eventually, Janet, too, decides to come out. "I'm heterosexual," she tells her friends, David and Sadie. "Does that mean you fancy me?" David immediately counters.
There are more questions: how do you know you're straight? What made you straight? There is a pause, during which David studiously examines his flies. "Could you imagine looking down and seeing that?" he eventually volunteers. "How would you know what to do with it?"
Janet also confides in John, who invites her to a straight youth club. After some initial nerves - "what if I turned out to be a rubbish hetero?" - Janet accepts. There, she witnesses her first boy-girl kiss. "I felt really naughty," she says. "Like someone was going to pull them apart at any moment."
Jeff Evans, a history teacher who works with schools tackling homophobia, believes that the film's power lies in exactly this reversal. "People's reality is given a derogatory twinge," he said. "It allows children to see themselves in someone else's shoes."
Made by Woking-based company Peer Productions, the film is available free to secondaries in Surrey. Teachers elsewhere in the country are able to buy the DVD for #163;85. It is being promoted by Schools Out, the organisation for lesbian, gay and trans teachers.