The first John Castle heard that a convicted paedophile had moved into a property abutting his school playground was when Evelyn, the chair of his parent teacher association, showed him a letter she had received.
On one side of the A4 piece of paper were photocopies of newspaper cuttings about the man's trial, some years previously. He had been convicted of interfering with a 5-year-old girl, the daughter of a friend. On the other side was an anonymous typed note informing Evelyn that the man had moved into the area and was now living in a flat overlooking the school playground.
Mr Castle's reactions were mixed. Some months earlier, the police had been called to the school after students and a teacher reported a man standing at a window, wearing what appeared to be a balaclava, staring into the classroom through binoculars.
The local community officer and the youth action team representative had dealt with it promptly by visiting the property and Mr Castle had heard nothing more. No more sightings were reported, even with the students keeping an avid eye on the flat.
"I felt in conflict," admits Mr Castle, who is head of a large urban comprehensive in the central belt. "I didn't know how to react when I was shown the letter. There isn't any guidance about this sort of thing; there is no textbook telling you how to react."
He deliberated over whether to inform the school board, the local authority and the primary school next door. Finally, he chose to discuss it with his local community police officer and the youth action team. Their advice was to leave it to the police and not mention it to anyone else.
"They seemed concerned about our end and asked if our chair could be considered secure," he says. "In other words, was she likely to discuss it with all her friends, and with the parents of her children's friends?"
Fortunately, on this occasion, Evelyn was in full agreement that it would be inappropriate to share the information with others. "I suspect the author of the letter sent it to me so that I would spread it among the parents, otherwise why not just go to the head?" she says. "The fact it was anonymous made me uneasy. It smacked of vigilantism. I felt only the school should know. I sent the note to our head and then left it up to him. He managed it well."
Strict vetting procedures are in place with school appointments, but headteachers have little control over who lives near their schools. There is, however, legislation in Scotland which means that certain sex offenders must notify the police of information about themselves, including their name and home address. Whether the police inform a school is decided by the circumstances of the case.
According to the Association of Chief Police Officers in Scotland, when their departments are informed that a sex offender is to be released into the community, they, along with social workers and other agencies, assess the risk that that person may pose. It is not common practice to inform schools.
"We do not as a matter of course inform the public that a sex offender is living in their community unless there are specific concerns or information that individuals may be at risk," says assistant chief constable Iain MacLeod.
"An offender who is forced out of a community could disappear, severing contact with the police and other agencies. Without monitoring or supervision, no stable address, and no clue to behaviour, the likelihood of reoffending is far greater than with someone who is closely monitored by the authorities."
The risk that a sex offender could be hounded out of his or her home by neighbours was enough to persuade Mr Castle to let the police deal with the situation. The stance taken by most local authorities and the Scottish Executive is the same: inform the police.
"Every school is surrounded by potential threats," says Mr Castle, "violent individuals, rapists or people with mental health problems. We can't be apprehensive all the time. And people need an opportunity to rehabilitate if possible."
His greatest challenge was to manage the reaction of his chair. "If Evelyn had not agreed to keep it quiet, I would have had to counsel her strongly about not spreading word of the letter and that could have been awkward,"
It has been some months since the communication and nothing more has been sent to the PTA or to the school.
Names have been changed to protect identities