The Niagara Catholic District School Board saying parents concerned about their children in the heat should contact schools directly.
The board says principals have been reminded that an Excessive High Heat Alert continues, and have been sent tips to prevent heat-related illnesses.
Each principal will use their discretion when it comes to gym classes, sports practices and any other outdoor activities until the heat alert is lifted.
We have reached out to the DSBN for its protocol during this extreme heat.
Meantime, unionized elementary school teachers in Ontario say this week's heat wave is taking a toll on students who are stuck in schools without air conditioning.
The Elementary Teachers' Federation of Ontario says the extreme temperatures affect children's ability to learn and can cause health issues.
The union is calling on the province to take steps to relieve the heat, which could include installing air conditioning systems or setting up cooling stations.
It says all schools should have a heat stress plan and a maximum indoor temperature limit after which they must take action, including shutting down for the day if necessary.
Much of southern Ontario is under a heat warning, with Environment Canada calling for temperatures above 30C.
Cooler weather is expected later this week.