Fifteen-year-old JJ lives with his mum, Anna, a self-obsessed estate agent who drinks too much. He doesn’t like her boyfriend coming round every weekend, smooching on the sofa with his mum. And his dad’s about to have a baby with his new girlfriend - JJ doesn’t see him much. “Parents are shit,” he’s decided.

He doesn’t like teachers either. He thinks they’re no good, and they think he’s lazy. So when his mum’s friends Paul and Jane arrange for their son Tom and JJ to have extra maths lessons, JJ isn’t happy. And when their tutor, Brian, reprimands him for not doing his homework, JJ decides to get his own back. He accuses Brian of molesting him.

Thankfully, none of this is true. It’s a work of fiction, the opening scenes of a play, The Maths Tutor, which receives its world premiere at the new Hampstead Theatre in London next Thursday. JJ’s accusation is not true either, although it’s enough to set in motion a drama that unravels the reality behind apparently ordinary relationships.

But the title and subject matter of the play invite comparisons with real-life stories and the human dramas behind them. Indeed, Hampstead Theatre’s artistic director, Tony Clark, commissioned playwright Clare McIntyre to write The Maths Tutor after hearing the story of a south London teacher who was forced to leave the profession after parents found out he was gay and objected to him taking their children on residential trips.

“It was three or four years ago, in a climate of fear about paedophilia, and making the spurious connection between homosexuality and paedophilia,” says Mr Clark. “Some parents heard that he was gay, and in the hysteria a parent complained, it went all the way to the governors and the teacher was suspended.” No specific allegations were made, and nothing was proven, but the teacher’s position became untenable and he left the profession with a severance payment and pension.

Coincidentally, he later read a newspaper report about an old friend (“somebody I hadn’t seen in years - we were in Christmas card contact”) who was accused, tried and acquitted of assaulting a young girl. “It took two years out of his life.” Tony Clark tried to make contact but hasn’t heard from him - or had any Christmas cards - since.

“Thematically, the play’s about the vulnerability of teachers,” he says, adding that gay teachers - like Brian - can be at particular risk of false accusations. “But it’s also about the pressures kids face in families where an apparently perfect relationship is less perfect than it seems. It’s about love, and it’s about young people and their relationships with older people.”

An added complication is that Paul and Brian are lovers, and it’s Brian who suffers when Paul’s wife Jane decides she can no longer tolerate her open marriage.

While The Maths Tutor is inspired by real life (research included noting the personal safety procedures of tutoring agencies, such as having another adult in the house and leaving doors open while teaching), it avoids the distressing but potentially dramatic areas of police interviews, courtroom trials and personal and professional crises.

When Tony Clark commissioned the play, this was the kind of scenario he had in mind. “I was expecting a big public play that had not only big classroom scenes but possibly governing board scenes and council scenes - a big David Hare-type job.” But he’s happy with the result. “It is a much more private play, although, I hope, with resonances that will make people think about the issues involved.”

Instead, the child’s accusation of sexual assault is made and dealt with in the space of a few scenes. JJ confesses that the allegations are pure invention and Brian confronts him. JJ’s motivation, Mr Clark suggests, is to get back at the teacher for humiliating him in front of his friend or to punish his mum for not telling him about his dad’s new baby. The allegations are never made public, the police don’t become involved and, apart from Tom and JJ’s class, the teacher keeps his job.

In real life of course, things are a lot messier. False allegations can wreck careers while serious abuse can go undetected and unpunished for years, with disastrous consequences. There is, says Mr Clark, “a big drama” to be made about that.

“I’m sure this play will be criticised on that level,” he says, “because people have a voracious curiosity about the procedural side of things, or for seeing a teacher disintegrate over time. It doesn’t show the public procedures - a documentary could do that better.”

Clare McIntyre is a past winner of the Samuel Beckett award and Evening Standard Most Promising Playwright Award, and The Maths Tutor is billed as “wryly comic, incisive and thoughtful”. Its title refers to the catalyst for the drama rather than its main character, but Tony Clark says teachers as well as parents will be able to relate to the dilemmas it deals with.

“I’ve worked in the theatre for a long time, and when people ask me why do I do it, I tell them that someone who has had a similar experience could come along, see a story that deals with that and be able to pitch their own experience against what they see. But I’m much more intrigued by doing stories for people who haven’t experienced it, so they can pitch themselves into a ‘what if?’ frame of mind: what if I was that teacher? What if I was that parent? What if I was that kid?”

The Maths Tutor previews September 25-27 and runs until October 25 at Hampstead Theatre. Box Office 020 7722 9301. It then goes to the Birmingham Rep from November 4. Box office: 0121 236 4455

FACT AND FICTION: HOW LIES CAN RUIN LIVES

On August 28, Alastair Wilbee walked out of his home in Shanklin on the Isle of Wight. He has not been seen since. Mr Wilbee, 47, was headteacher of Summerfield primary school in Newport, but in May he was suspended following a pupil’s allegation of sexual assault. Details of the allegation, which Mr Wilbee strenuously denied, were due to be published in a local newspaper the day after he vanished.

His disappearance also coincided with the Hutton inquiry into the alleged suicide of arms expert Dr David Kelly. Mr Wilbee’s wife, Gail, herself a teacher, fears he may also have taken his own life. “I watched the news about the Kelly inquiry and listened to the suicide experts and I watched my husband go through those same stages of loss, grief and powerlessness.”

She says he felt “deep grief at the waste of his professional life and the loss of standing in the community that he saw as the inevitable result of the publication of his name. My husband’s suffering has highlighted the vulnerability of professionals working with children.”

Teachers and others who are the subject of malicious allegations could soon be spared the indignity of having their name made public. The Home Office announced its intention earlier this month to amend the Sexual Offences Bill going through Parliament, to prevent identification until a charge had been made. This follows several high-profile allegations of sexual offences in which the defendant has been acquitted or charges dropped.

Every year several hundred teachers are accused of sexual or physical assault by pupils. Reputations are not the only cost; a BBC survey three years ago estimated that around pound;4 million a year was being spent on supply cover and salaries for suspended teachers.

In July, the Professional Association of Teachers conference heard that the number of assault claims against its members had risen to 36 in the first five months of the year from 30 in the whole of 2002 and 19 in 2001, and that the “overwhelming majority” proved unfounded.

The National Association of Schoolmasters Union of Women Teachers says less than 5 per cent of cases end in conviction. Between 1991 and the end of 2002, 62 out of 1,557 cases led to convictions. Up to August this year, 119 allegations had been made against the union’s members. No further action was taken in 52 of them and there have been no convictions; the rest are still being investigated, a process that can take up to seven years.

In 2001, the Department for Education and Skills appointed 26 regional investigation and referral support co-ordinators to ensure that allegations are dealt with speedily.

Martin Pilkington, head of legal and member services at the Association of Teachers and Lecturers, says delays in dealing with cases “are a matter of grave concern”. Allegations of physical or sexual assault are, he says, “now regrettably a constant feature of teaching. It is one of the major neuroses within the profession, especially for male teachers.”

Even when charges are dropped or the teacher acquitted, those who return to work have to live with the stigma. “Nobody ever really clears their name,” says Mr Pilkington.