About a dozen students at Georges Vanier Catholic Elementary School in Brampton, have had their Christmas vacation extended, after they started feeling sick.
The students complained of illness after returning to the school on Monday.
Some said they had headaches, one said she had trouble breathing.
One parent, Jennifer Valenti, said the health problems may be connected to renovations carried out recently.
She said some of the workers were dressed in hazmat suits and there were sealed bags left in the dumpster.
Valenti said she asked the principal and she "was assured by [the principal] that ... the school is safe, there's no asbestos in the school."
But parents say the Peel-Dufferin Catholic District School Board has been secretive.
When contacted by CBC News, the board said it was working on a letter to send to parents.
Bruce Campbell, a spokesman for the board, said the floor tiles do contain "trace amounts of non-friable asbestos."
The University of Toronto's environmental health and safety website describes non-friable asbestos tiles as those in which the asbestos fibres "are not easily released."
"Such a product would present a risk for fibre release only when it is subject to significant abrasion through activities such as sanding or cutting with electric power tools. Examples of non-friable asbestos products include vinyl asbestos floor tiles, acoustic ceiling tiles, and asbestos cement products," the website says.
Marcello Ponciano, who specializes in asbestos removal, agrees the tiles pose little risk, but he believes parents should have been notified.
"It's always a concern," he said, when it comes to "children, health and safety."
The Ontario Ministry of Labour has conducted air quality tests, but the results won't be available until next week.
Valenti says until then her daughter will stay home.