The police have sole responsibility for deciding whether parents should be told when a sex offender has moved near their children's school under new guidelines agreed with headteachers.
A protocol agreed by the National Association of Head Teachers and the Association of Chief Police Officers means heads will follow advice from police on how widely they disclose sensitive information about paedophiles.
The move follows the Sex Offenders Act 1997 which obliges paedophiles to keep police informed of their address. In some cases - if an offender moves near a school or playgroup or is seen in its vicinity and police fear he is a risk to children - the headteacher or playgroup leader may be told.
But heads feared being left in the uncomfortable position of deciding what to do with sensitive information without professional advice. Both police and heads are keen to avoid the risk of vigilantes or a repeat of the kind of scenes seen in Bristol and Somerset following the release of paedophile Sidney Cooke earlier this year.
"Police have prime responsibility under the Act - that is crucial," NAHT general secretary David Hart said. "They will make the decision about what information about sex offenders should be passed onto a third party."
That would include advice on whether other teachers, parents and governors should be informed. In some cases only individual teachers or parents might be informed - in other cases all or none would be. Names have been passed on to heads three times since the Act came into force - the NAHT says one, in the south of England, was badly handled.
Liz Pavey, outgoing NAHT president, said police and heads must act in a "partnership of confidentiality". "We are not setting our members up to scaremonger in any way," she said.