I think there is a lot more flexibility in the elementary years, because there's the ability to pick up next year (except for grade 8s), But the high school years are so defined by subject and learning the curriculum, that I think it would be hard to teach twice the curriculum next year.
My son is in grade 12, too. He was finally on track to get some really great marks this semester and that momentum may have been derailed, now.
Our teachers have reached out, too, but so far, it was just to post reminders to complete existing work and that "something will be coming". I hope so.