The World Health Organization says there is no convincing scientific evidence that wireless networks cause any damage to human health. Yes, wireless devices emit electromagnetic radiation, as do other electronic devices we use in our homes and offices: computers, televisions, even baby monitors. The exposure to radiation from a mobile phone, which is generally much closer to the person using it than a wireless access point, is much higher than that from a wireless network.
It’s certainly true that exposure to wifi networks has increased over the past few years, and that it might take time for any ill effects to show up in the research. So it makes sense for health agencies to keep monitoring the research and be prepared to change their minds, as is true for all science. The evidence from the research to date, though, is clear and reassuring. There is certainly no reason to start getting rid of wifi in schools and other places where children spend a lot of time.
The WHO fact sheet on wireless networks is here. More recently, Health Canada posted the following video.