Teachers want an investigation into whether there are any health risks from wireless computer networks in schools.
Teachers want to clarify the safety of wireless networks
The PAT teachers' union is writing to the education secretary for a clarification on wi-fi safety.
"There's a concern the potential health risk of this technology hasn't been investigated fully," says the union's general secretary, Philip Parkin.
The Health Protection Agency says "wi-fi devices are of very low power, much lower than mobile phones".
Mr Parkin, leader of the Professional Association of Teachers, is writing to Education Secretary Alan Johnson to ask for a "full scientific investigation into the effects of wi-fi networks in schools".
"I am concerned that so many wireless networks are being installed in schools and colleges without any understanding of the possible long-term consequences.
"I am not saying there is a danger, but I have enough concern to ask for it to be investigated."
The union highlights the case of Michael Bevington, a classics teacher at Stowe school in Buckinghamshire.
Mr Bevington "had never had any problems before the wi-fi. When it was put into his classroom he suffered nausea, blinding headaches and a lack of concentration. When the school removed the wi-fi his condition improved".
Many primary and secondary schools use wi-fi networks - but the teachers' union believes that there is insufficient long-term evidence to show whether such networks are safe.
The Health Protection Agency points to the low power levels of such wi-fi networks, compared to mobile phones.
But while the HPA declines to back health fears about wi-fi, the agency also offers no clear guarantee of its safety.
In a statement, the agency says its chair Sir William Stewart, is being "pressed by lobbyists to condemn wi-fi and is unprepared to do so. He has not taken a position on wi-fi".
"The HPA and Sir William have always pressed for more research into these new technologies. The only firm precautionary advice issued by the HPA is about children's use of mobile phones."
The need for greater research into health hazards from such technology is reflected in the minutes of an HPA meeting last month - where on the issue of "electrosensitivity" it was said that "scientific investigations conducted so far very seldom give clear answers".
A two-day meeting of experts on electrosensitivity, with a "political and scientific remit", was proposed by the HPA for early next year.
Studies for the HPA have so far been unable to confirm or disprove claims about electrosensitivity.
Part of the problem for researchers is that it is difficult to isolate the individual effect of technology such as wi-fi networks - when people might also be exposed to more powerful signals, such as from mobile phones.