Schools across London are to fight crime using a new paging system. They will use pagers to alert each other to vandalism, burglaries or suspicious characters outside their gates.

School Watch, launched in the borough of Harrow yesterday, is designed to cut down on theft and criminal damage which costs each school pounds 2,200 per year on average. Nationally such crimes cost about pounds 49m, with one school in eight the subject of arson attacks.

More than pounds 1m of damage was caused in Stockport, Greater Manchester last April by arsonists who attacked seven schools over a distance of 5 miles in one night. The London scheme could prevent such serial attacks.

Head teachers will be able to pass messages to one another via pagers. Police will also be able to convey warnings and tap into information put out by schools.

All of Harrow's 70 schools have agreed to pay pounds 3 per week to take part in the project. Most have been victims of theft and vandalism, and some have suffered arson attacks.

The project was adapted from a programme used by London pub landlords to warn each other when they have ejected troublesome drunks, on the assumption that such people would be likely to look for alternative drinking spots in the same area.

School Watch is run jointly by the Metropolitan Police and education authorities, and it is hoped that it will spread to all London boroughs. Both head teachers and the police can telephone information 24 hours a day to a bureau which transmits the information on to a small screen.

Janet Evans, head teacher of Priestmead First School in Harrow and borough co-ordinator, said the first priority was to ensure children's safety. Any suspicious character deterred by staff from hanging around outside was likely to move on to another school in the area.

While Priestmead was not particularly hard hit by crime, she said it had suffered minor damage by vandals and trespassers, and staff handbags had been stolen by intruders who simply walked into the school on more than one occasion.

'We have had people sitting in cars or wandering up and down the road in the past, and if it didn't feel right we rang the police. But these people can be across the borough in 15 minutes and in another school if they feel they have been sussed out here. That's why it's important to get messages through quickly,' she said.

Sir John Smith, Deputy Commissioner at New Scotland Yard, said he welcomed the collaboration.