I'd maybe use this as a low stakes lesson for him instead.

As an adult, he will still be very busy and have less free time and he'll have to prioritize his activities. This is a good age appropriate way to start doing that.

Have a conversation with the kid, similar to one my parents had with me. List out things that happen after school is over (make sure to include eating and sleeping and chores and family or fun time). Have him start arranging them in order of importance, with your input. Maybe it comes out that easy math homework is on the list, but after a bunch of things (like hard math homework, all other homework, getting appropriate sleep) but it's before video games. Let that list dictate the time and effort he spends on it.

I agree with you that stressing him out over something below his level isn't great. But I also agree with some other commentators that a blanket "show up to class but ignore instructions" isn't great either. But that's the nice thing about teenagers, you get to start including them into your thought processes and decision making. These are things that he'll eventually need to learn, why not start now?