Generally you'll do better with a carrot than a stick.

I see the argument for the time requirement on beginners, you have to teach them how to practice and what it takes to get better. That's nearly impossible to really enforce. Practice logs lead to lies. Kids will put down what you want to see, and parents will sign off on it to keep their kids out of trouble. Open the band hall before and after school. Yes, that's extra time for you. Be available to help them, make it positive and fun. Bring donuts sometimes.

Find a way to incentivize the kids who do put in the work. That tends to work better if you look at results rather than time on task. Give the kids playing tests in class for grades. Have the kids do recording assignments. They'll do it over and over again until they get it right...sounds a lot like practicing (I know, practice until you can't get it wrong...). Do passoffs and put a sticker chart on the wall (if that's allowed at your campus). Offer rewards for kids who do a certain number of passoffs or meet some other musical standard. It's amazing what kids will do for some pizza.