James, a middle-aged, happily married Year 8 form tutor was marking work when a group of girls came into his classroom. They looked over his shoulder at his laptop, where the screen-saver showed a picture of his family. In the ensuing conversation, James showed them other family snap-shots saved on his computer, including one of his toddler laughing in the bath. Days later James was suspended from work as police interviewed him on suspicion of grooming the girls for sex.

The teacher, whose name has been changed, is still suspended as investigations drag on, despite the fact that he has his headteacher’s backing. Social workers acquainted with the case are astonished that it was ever brought.

It’s too late to help James, but the guidelines designed to speed up the investigation of allegations against teaching and support staff is at least a step in the right direction, says Chris Keates, general secretary of the NASUWT union. “Too many innocent teachers have had their lives and careers wrecked by false allegations of abuse,” she says. “Teachers and others who work with children are extremely vulnerable to false allegations.”

As children have grown more savvy, the number of such incidents has grown, even as convictions have fallen. Getting Sir or Miss into trouble of their own is sweet revenge indeed for a string of detentions. But speeding up the investigations is only part of the answer. The difficulty of providing clear guidelines for teachers means that they find themselves negotiating what one calls a “sexual minefield” every day.

Michael, a newly-qualified Spanish teacher at a girls’ grammar, says that although he was highly aware of the usual pitfalls nothing could prepare him for how completely unabashed the girls - especially the younger ones - were in front of him. “I’d walk in to take a class and, bam! One child in the front row would have her shirt over her head as she peeled her sweater off. Another was hoiking her skirt up to show her mate her hold-ups.

Another was showing off her bra. I used to flee. Sometimes I still have to walk out for a minute, before coming back in to start the lesson.”

He still wonders whether the girls, used to a single-sex environment, simply don’t think of him as a man, or whether he’s actually the butt of a collective teenage joke. So the old rule “never be alone with a child” is not always a help.

It wasn’t for James. He was not alone with one child, and although there was no other teacher in the room, the door on to the corridor was open. For James to have been safe, he should not have shown his pupils family snap-shots. But this sort of caution risks freezing out the warmth and spontaneity that for many teachers saves the job from being akin to working on a sausage machine.

Indeed, the latest recruitment drive emphasises the human side of teaching and the satisfaction to be gained from a good relationship with lively young minds. But, say some, absolute peace of mind is only bought at the price of throwing a cordon sanitaire around yourself with big Keep Out signs. And, they say, this is too high a price to pay.

Ellen Jones, a primary teacher, is leaving after 25 years, saying that fear over “misunderstandings” has drained all the satisfaction from her job. “I am naturally a touchy-feely, motherly kind of person. That’s what attracted me to working in the primary sector. I can’t refuse to give a crying child a cuddle, or to pick up a little one that’s fallen over and hurt himself,”

she says. But Ellen has recently had “one or two unpleasant instances”; the first where the parent of a child with behavioural problems, whom Ellen had often comforted after scrapes in the playground, complained about her using “any excuse to touch my child”. In reality, Ellen had physically restrained the child from attacking a classmate. This was followed by a warning, albeit in sympathetic terms, from her head that she was not to touch the children unless absolutely unavoidable, and then only in view of another member of staff.

“I can’t do my job like that, with the grubby sort of thought that that behaviour implies,” she says.

And here lies the rub: the whole field is so subjective that once you rule out grossly inappropriate behaviour that is clearly unacceptable to anyone, teachers and support staff are left casting around in a grey area of second-guessing what children, parents or, indeed, colleagues, may consider inappropriate.

Mary Shaw, recently retrained as a secondary English teacher after a career in business, found this to her cost after an outing to London. When one of her Year 10s realised his father was not at the pick-up point on their return, Mary and her colleagues had to decide what to do. The rest of the boys were continuing on the coach to school, but leaving Johnny to wait for his dad alone on the high street at 11.30pm was not an option. It was decided that Mary should wait with him. The father arrived and all was well.

Until the next day, when the head summoned Mary to tell her - and her more experienced colleagues - that such behaviour was unacceptable.

“The head was in a state of barely controlled panic at the thought that I’d been in a potentially compromising situation with the boy.

“My initial reaction was a mix of amusement and bemusement - at the grand old age of 42, I’ve got a son my pupil’s age; I did what I would have expected my son’s teacher to do.”

The point, the head said, was that another teacher should have remained with Mary, even if it meant leaving cover short for the other children on the coach.

“The ‘never be alone with a child’ option is, in practice, not possible in so many instances,” says Martin Ward, of Association of School and College Leaders (formerly the Secondary Heads Association). “What do you do if you’re on a trip, and you’re the only one who can help the child, or marking in the class-room and a child appears at your elbow? That’s one reason we never give specific advice on this. It’s an extraordinarily difficult situation.”

The bottom line is that ultimately, you, the teacher, have to make judgment, taking into account the situation, the nature of the child, the “never be alone” rule and your own natural “gut feeling”. The only consolation, if you get it wrong, is that under the new disciplinary guidelines, you won’t face automatic suspension.