With everything that has been said here, remember that you need to teach them a way practice. A nebulous 20 minutes at home can quickly turn into chaos for families who might have no clue what is going on with their kid and the clarinet mouthpiece/barrel.

I like giving students a check sheet of things to do at home and then have parents sign off on each thing. It doesn't have to have a time attached to it and can be simple enough that the kids will feel confident and excited to show their parents because they are successful doing it in class.

Make it idiot proof, "Open your case at home for someone at home and name the parts of your instrument". "Play a rhythm line on your mouthpiece/head joint/practice pad for someone at home". "Show someone at home how to hold your instrument like in the picture on the page".

By the time get to more challenging things, students already have shown parents a bunch of different things on their instrument, and you will probably have an idea of which kids are actually completing the assignments and which kids aren't.

If families are against the kid practicing, give the kid the best possible experience and then have a conversation with them if they want to continue band next year.

Good luck with your year.