About 40 people, including a dozen kids from Grades 1 to 5, joined a picket line outside the York Region District School Board offices in Aurora, spokeswoman Christine Marrin said.
Parents are concerned that Wi-Fi could be exposing their children to radiation six hours a day, five days a week, for 40 weeks of the year, she said.
"There have been no studies on children to determine whether that level of exposure for that length of time is safe," said Marrin.
Earlier this year, the World Health Organization warned about a possible link between radiation from wireless devices such as cellphones and cancer.
Some believe wireless access to the Internet could pose similar risks. But while Health Canada cautioned parents to limit the use of cellphones by children, it said that based on scientific evidence, low-level exposure to Wi-Fi is not dangerous.
Marrin says it's too early to make that determination.
"This is the first generation of children that has been in that particular learning environment, so how Health Canada can say that it's safe is really quite a mystery to us," she said.
The Ontario government said in June it would examine the WHO warning but wouldn't take any immediate action to require warnings on wireless devices. The legislative buildings in Toronto will themselves soon have Wi-Fi.
Ontario Education Minister Laurel Broten says it's up to school boards in the province to make decisions about whether to use Wi-Fi or not.
"The best available information clearly indicates at this point in time that it is safe," said Broten.
"I am not a scientist but I can tell you it is important to us that our schools are safe and we believe that school boards each and every day make decisions to make sure that kids are safe in their schools."
NDP Leader Andrea Horwath says she realizes many parents are concerned about the issue.
"It's worth keeping an eye on," she said.
Some Canadian private schools and at least one public school board in British Columbia have removed or strictly limited Wi-Fi due to safety concerns. But York Region and many other public school boards across Canada continue to use it.
"They are very firm in their position, they are standing behind Health Canada's assertion that Wi-Fi is safe for children. Of course, we disagree," said Marrin, adding the concerned parents have been asking for a face-to-face meeting with the York board.