I've never used emergency sub plans, because even if I'm deciding the day of that I'm not coming in, I can still write up a plan, email it to my admin and have it carried off. Usually for sub plans I use videos, because they take up the entire period, it's easy for the sub, and doesn't require special preparation. However with block periods, my go to videos no longer cover the entire period (Cosmos: they're only 50 minutes each). Also I'm wondering if there might be something better. I can't think of enough worksheets that would use up 90 minutes of class time. Any ideas?