Parents of students at 15 Ottawa schools might want to check their children's knapsacks tonight. According to the Ottawa-Carleton District School Board, three high schools and 12 elementary schools have infestations of cockroaches.

However the OCDSB is only notifying parents of one of those schools about the infestation, and plans to inform the others "over the next few days."

Heather Birchall is angry she was not informed earlier about cockroaches at her children's school. (Steve Fischer/CBC) Parents of children at Manor Park Public School were the first to receive notice Thursday. According to the email, the warm summer and a renovation project at the school conspired to provide perfect breeding conditions for the bugs.

The school says it's been dusting the building with a mild pesticide for the past couple of weeks to try to get rid of the cockroaches, but is now planning a more thorough spraying over the Thanksgiving weekend.

Parent upset she wasn't informed earlier

Heather Birchall has two children at Manor Park. She's angry she wasn't informed at the start of the school year.

"Our children could have been carrying these [cockroach] eggs home for weeks now and infesting [the homes of] people, and I don't think it's right that they withheld this information from us," she said.

I don't think it's right that they withheld this information from us. - Heather Birchall, parent

The OCDSB said schools do not normally inform parents when they're dusting for bugs because the pesticide is not airborne, may be confined to one small area of the school and is mild enough that it poses no health risks.

But schools do inform parents when they plan a more intensive spraying campaign. The board says the other 14 schools with infestations will be informed over the next few days, and parents will be told to take precautions to prevent the bugs from "hitchhiking" into their homes.

The board's superintendent of facilities Mike Carson said the board wants parents and staff to be vigilant.

"We encourage parents to check your kid's backpack," Carson said.