As a former coach in a rural school, this was such a problem, especially with maintaining weight and conditioning.

We came up with a very fun routine when school was cancelled. We could not practice, but the basketball team could,,,never figured that one out. Anyway We went sledding on a very steep hill near one of the kids farm. I staked out a rope, it was amazing, the guys would go up and down that hill all afternoon, we got a good cheap workout that even the biggest fishes participated in.