Almost half of the thousands of allegations made against school staff each year turn out to be unfounded, according to the first government-commissioned study of its kind.
A total of 47 per cent of the claims made by pupils and their families were unsubstantiated or malicious, the nationwide research revealed. At the other end of the scale, 12 per cent of more than 2,800 allegations led to a police investigation, with 3 per cent resulting in a conviction or a caution.
The findings, which relate to cases dealt with by local authorities between April 2009 and March 2010, come after ministers announced plans to give anonymity to teachers facing allegations. But the statistics, published last month, have prompted renewed warnings about the suffering endured by staff when facing accusations that turn out to be false.
Teachers who undergo a police investigation often find that the action ruins their career, according to Chris Keates, general secretary of the NASUWT teaching union. She wants all police forces to make it clear on Criminal Records Bureau (CRB) checks whether an accused teacher has been exonerated.
"At the moment, the whole system is fragmented and there is too much variation in practice," Ms Keates said. "An allegation can follow a teacher for the rest of their career, even if it is unsubstantiated. If it is recorded on a CRB form, the view of a governing body is there is no smoke without fire."
According to the study, 28 per cent of allegations resulted in disciplinary proceedings against school staff, with 6 per cent leading to dismissal. Another 4 per cent of teachers quit.
Amanda Brown, the NUT's head of employment conditions and rights, said police investigations were often instigated by parents after schools had ruled out that course of action.
"There are parents who go to the police to make an accusation, rather than the school, in cases where school leaders would not have thought this was necessary," she said. "Teachers subject to accusations can feel as if they are on a treadmill if someone doesn't make a decision early on about how serious the complaint is. It makes it more difficult for decisions to be made because the longer it goes on, the implication is that there must be something to it."
Brian Lightman, general secretary of the Association of School and College Leaders, said that headteachers were powerless to prevent families from going to the police with malicious allegations. "There is now a tendency for parents to believe everything their children say, as opposed to what the teachers are saying," he said.
Centralised national data are not routinely collected on the number and nature of allegations made against school staff that are referred to local authorities. The only previous research drew on a smaller-scale study in 2007, which looked at complaints made over a six-month period.
More than half of the allegations against school staff in the most recent study were in relation to physical abuse, while 19 per cent related to sexual abuse and 11 per cent were about misconduct, including inappropriate language or behaviour.
The survey found that 17 per cent of allegations of physical abuse were made after teachers had used authorised restraint on pupils.
Last year's Education Act gave teachers a legal right to anonymity in cases where claims are made by pupils, until the point at which they are charged with a criminal offence. The law, designed to stop publication of allegations by newspapers, is due to come into effect "at the earliest opportunity", a Department for Education spokeswoman said.
2,827 allegations were made against school staff between April 2009 and March 2010
45% were unfounded or unsubstantiated
2% were malicious
56% related to physical abuse
12% led to criminal investigations
3% led to convictions or police cautions.