The key reference agencies in this matter are Becta and the Health Protection Agency and the following note contains some background information from them that you may wish to consider

Summary
There is no evidence to date that exposure to the radio frequency (RF) signals from WiFi and WLANs adversely affect the health of the general population. In addition, Health Protection Agency advice is:
• The signals from WiFi are very low power, typically 0.1 watt (100 milliwatts) in both the computer and the mast (or router) and resulting exposures should be well within internationally accepted guidelines.
• The frequencies used are broadly the same as those from ‘traditional’ RF applications.
• Based on current knowledge, RF exposures from WiFi are likely to be lower than those from mobile phones.

On the basis of current scientific information WiFi equipment satisfies international guidelines. There is no consistent evidence of health effects from RF exposures below guideline levels and therefore no reason why schools and others should not use WiFi equipment.

“Following Monday night’s (21 May 2007) Panorama programme, Becta has been in contact with the Health Protection Agency (HPA) – the government agency responsible for health and safety – to obtain the latest guidance on any health issues relating to wireless technology.

Despite the claims made in Monday night’s programme, the HPAs guidance remains the same. The latest advice on their website reads:

“On the basis of current scientific information WiFi equipment satisfies international guidelines. There is no consistent evidence of health effects from RF exposures below guideline levels and therefore no reason why schools and others should not use WiFi equipment.”