Wireless computer networks in schools may pose a significant health risk to children and staff, a teaching union warned today.
Many teachers fear the radiation emitted by wireless transmitters could be contributing to poor concentration and hyperactive behaviour among pupils.
One school - Stowe School, in Buckinghamshire - has already dismantled part of its wireless connection after a teacher fell ill, complaining of headaches and nausea.
The Professional Association of Teachers has written to Education Secretary Alan Johnson to demand an inquiry into the effects of the technology, which is being installed in classrooms across the country.
The union's concerns are echoed by Sir William Stewart, chairman of the Health Protection Agency, and a former chief scientific adviser to the Government, who has chaired two official inquiries into the hazards of mobile phones.
Sir William is said to be "very keen" that pupils are monitored for potential health problems.
Wireless, or wi-fi, systems, use a small transmitter to link laptop computers to the Internet without the use of cables.
Installed in up to 80 per cent of secondary schools and more than half of primary schools, they are also used in coffee shops, hotels and airport departure lounges, and have become a fixture in millions of homes.
The system has created a cloud of 'electronic smog' across
Britain, scientists say. There are fears that the networks could be doing untold damage to health.
Campaigners claim the level of microwaves emitted by a wireless transmitter is comparable to that from a mobile phone mast.
They point out little or no research has been carried out into the technology's side-effects.
Problems including headaches and lapses in concentration have already been reported by those who use wi-fi systems frequently.
Some scientists fear they could also cause cancer and premature senility. Children, whose brains and bodies are still developing, may be particularly vulnerable.
Alasdair Philips, of campaign group Powerwatch, believes the radiation from wireless networks is partly to blame for the rise of behavioural problems such as attention deficit hyperactivity disorder or ADHD.
He said: "I believe that rolling out wireless networks in schools should be a criminal offence without close monitoring of pupils' health.
"Being in a wi-fi classroom is similar to sitting in the main beam about 330 feet from a mobile phone mast.
"The problems that many teachers are reporting, such as poor concentration, and the four-fold increase in ADHD in the last ten years are exactly the problems we would predict."
Philip Parkin, general secretary of the Professional Association of Teachers, said he was concerned about the health of both pupils and staff.
"The proliferation of wireless networks could be having serious implications for the health of some staff and pupils," he said.
"I am not saying there is a danger, but I have enough concern to ask for it to be investigated."