Research claiming that one in 10 American children has been sexually exploited at school - and that almost half the abusers are women - has shocked parents as one of the nation's most notorious pupil abusers is about to be released from prison.
More than 4.5 million school-age children have been subjected to some form of sexual behaviour from teachers or other adults meant to be looking after them, said the first official research commissioned by the US government's education department.
The Washington State Corrections Department said that Mary Kay Letourneau, who had two daughters with her pupil lover, will be freed early next month after serving more than six years for statutory child rape. Letourneau, who first had sex with the boy in 1996 aged 35, when he was 13, will remain on the register of sexual offenders.
Meanwhile, a 23-year-old middle school teacher gave herself up to police in Ocala, Florida, to answer allegations that she had sex with a 14-year-old boy pupil five times last month. Debra Beasley Lafave, a former model who has appeared in several racy magazine photo-shoots, faces up to 15 years in jail and a fine of $10,000 (£5,400) on each charge if convicted.
The report, written by Charol Shakeshaft, a professor at New York's Hofstra University with more than 25 years' experience in schools research, analysed information about incidents ranging from inappropriate sexual comments and jokes, or the passing of notes, to physical sexual abuse and child rape.
It said teachers were responsible for 18 per cent of all reported incidents of sexual misconduct, with sports coaches, substitute teachers, bus drivers and classroom assistants the next most common offenders.
'It's often the most popular teachers who are responsible,' Shakeshaft said. 'Parents have to pay attention and ask questions. Is this person driving my child home from school? Are they helping them out with their work a little too closely?
'Most of the time there is no problem but if parents educate themselves to know what they are looking for, inappropriate behaviour is observable. I've always watched my daughter to see if any relationships with her teachers are a little too close. I listen to her and make sure there's no crossing of boundaries.'
The report was criticised by representatives of school employees, although they did not deny there was a problem. 'Lumping harassment together with serious sexual misconduct creates unjustified alarm,' said Michael Pons, spokesman for the 2.7m member National Education Association.
Paul Houston, director of the American Association of School Administrators, said: 'You're talking about a small number who are doing these inappropriate things out of millions of teachers and millions of employees.'
Others believe that the figures might even be higher than reported because many pupils are too frightened to speak out.
'Children must be very clearly educated about inappropriate behaviour, and so must the teachers, so when children see the signs of this behaviour they have someone to tell,' said Professor Bob Shoop, a lecturer in sexual exploitation in schools at Kansas State University.
The Education Department said it will study Shakeshaft's report closely. The department's deputy secretary, Eugene Hickok, said: 'We believe that sexual misconduct in whatever form it takes is a serious problem in our nation's schools and one about which parents have a right to be informed. The overwhelming majority of America's educators are true professionals doing what might be called the essential work of democracy. The vast majority of schools in America are safe.'