This will be school-specific. In any case, the returning officer will have to work with the local schools to decide whether or how the facilities can be set up to avoid commingling students and the general voter population. I expect that in a pandemic, many schools would not be open for us to use as polling places. Certainly in Ontario they've given that indication if it's on a Monday. Other provinces.... Manitoba has said the same.
When the election takes place, whether the vaccination is rolled out completely or whatever the situation is, I'm certainly not counting on schools. That's why we have to look at alternative places.