ONE OF Maria's colleagues at the middle school where she used to teach was arrested a year ago when police found child pornography in his house. Since then, Maria has come near to a nervous breakdown and has taken it upon herself to apologise to all those parents whose children she put at risk by recommending the school.

She does not try to hide her pain. 'I felt shattered. Five years of my life turned out to be an error of judgement. It was happening under my nose and many were in great distress and I didn't do anything.'

Some of the children were already from emotionally vulnerable backgrounds. 'For many, it was lovely to be touched. They needed it badly and for some it was very beneficial. For the staff, it was very difficult to draw the line between what was proper and what was not.'

Mostly, she tells herself, the teacher's behaviour was borderline. 'But I have to suspect the worst. He was collecting pornography for years. He only had to wrong one child and that child would be scarred for life.'

Maria did not initially suspect abuse, even when children eventually complained to their parents that they did not feel safe when they were alone with the teacher. She says now: 'You see it if you know what to look for, but if you haven't got the framework into which to fit all the information, you interpret it differently. There was a certain wildness in the children at times which I now know is one of the signs. I did go to the deputy head but her experience was not broad enough to imagine it could possibly be the case. I felt quite helpless because I didn't know which way to turn.'

In this Maria is not alone. Often in cases of suspected abuse teachers and heads do not know how to proceed.

This week the six teaching unions and the local authorities will launch national guidelines with procedures for dealing with such allegations. The guidelines will be sent to all their members. They are a direct result of unions' concerns about the increase in false allegations made against teachers.

The extent of the problem is difficult to gauge. Only the National Association of Schoolmasters/Union of Women Teachers, one of the larger teaching unions, has separated figures for alleged sexual abuse from those of physical assault.

These show that in 1993 there were 57 cases of alleged sexual abuse, and in the first five months of this year there were 29. But all the unions talk of an increase in desperate phone-calls to their lawyers for advice about allegations. The Department for Education has recently sent questionnaires to all local authorities to establish an accurate picture.

Chris Keates, an executive member of Nasuwt, says: 'We do not seek to protect child abusers but we do need to protect teachers who have their lives shattered by pupils.'

The guidelines are understood to recommend that heads should carry out a quick initial assessment to see whether the incident could logistically have happened. Heads sometimes panic and suspend the teacher on the spot only for it later to turn out that he was not even in the school on the day the abuse was alleged to have happened. The guidelines will also call for greater liaison between the various agencies involved - social services, the police and the Crown Prosecution Service.

It is hard to appreciate the devastating effect that such allegations can have on the accused teacher. Tim was 39 when his career ended abruptly at a girls' secondary school after three girls accused him of 'touching our bums'.

Although there were witnesses to say it could not have happened and the girls' testimony was inconsistent, Tim was arrested at school despite the head's protestations and without listening to any of the witnesses. It was a year before the case came to court. Tim was cleared by the jury in 10 minutes, but did not return to teaching.

Tim's wife, who taught at the same school and also gave up her job, feels bitter. 'It is impossible to prove innocence and one's good name and self-esteem are irreparably damaged.

'The girls left the school the day after making the allegations, but we get no compensation for loss of earnings after 40 years teaching between us.'

Some may feel that the unions are still not dealing adequately with cases of genuine abuse. Governors at a north of England inner-city primary were horrified to learn that one of their teachers had been allowed to carry on rubbing pupils' bottoms and looking up their skirts for three years despite complaints from children, parents and new teachers. The first complaint about this teacher had been made to the head in 1990, and yet on retiring he had given the teacher glowing references.

Nine members of staff knew what was going on but decided to ignore the complaints, including one who had herself witnessed one of the episodes and noticed the look of horror on the child's face. Why take so long to come forward? An adviser involved with the case said: 'Staff do not act against their own colleagues.'

Moreover, in cases like this where the trauma of putting young children in court could prove more damaging than the original abuse, the police generally decide not to prosecute. It is then left to the school to proceed with internal disciplinary hearings.

But unless caught in flagrante or if there is some physical evidence of abuse, it is very difficult for inexperienced governors to prove the teacher's guilt, especially since parents often refuse to allow their children to testify.

Teachers who are members of a union can be provided with an experienced lawyer to put their case at the disciplinary hearing. 'This leaves an unequal balance of power,' said one parent governor about the case she was involved in. 'He sometimes went for witnesses in an unacceptable fashion, intimidating them, harassing them. I think it's wrong that inexperienced parents and governors are put under that stress.'

After her experience, she feels that the local authority should take on such cases, not the governors.

'These hearings expose the bankruptcy of the Government's policy,' commented a spokesman from Nasuwt. 'Parents interested in their children's schools do not have the necessary expertise to discharge all the governors' functions.' Officials from some unions admit that their lawyers will not pull out all the stops if they believe the teacher is guilty.

In the case of the north of England primary school, the union lawyer cited a 'low level of sexual abuse'. Are governors to tell parents that 'low levels of sexual abuse' are ignored in the schools where they send their children with the expectation that they will be safe?

Shockingly for parents, London teenagers seem to take for granted that harassment is a normal part of secondary school life. At one school, a sports teacher - who has since been arrested - was well known for having affairs with 16- and 17-year-olds. But, as one girl said: 'We all knew it and the girls would always go into the changing rooms in couples to be safe. And he was an excellent coach.'

Names in this article have been changed.