Yes, that's how it works in Alberta. It's particularly confusing because not all schools have the same academic calendar (e.g., most schools have a summer break, but a few have summer classes).

Unlike the sibling comment, there are no lights or indications of when school is in session. You must memorize the academic calendar of every school you drive past in order to know the speed limit. In practice, this means being conservative and driving more slowly in unfamiliar areas.