We have done before school rehearsals on the days we didn't have band. In addition, in years past we had an ensemble class and those students that weren't in Athletics (Double blocked of course) Students were supposed to sign up for ensemble class if it could fit in their schedule.
We finally moved away from block last year, only for it to come back this year due to COVID. Now it's worse. Block every other day, no ensemble class. Definitely reading below what we have in the past.
We have also done flipgrid assignments where they just record themselves practicing for 10 minutes (since that is the max it will let you do), just so we knew they were at least doing something.
Best of Luck!