Ah, I get it. Honestly, I cannot blame him for having prioritized his most important work and ECs over busy work homework that didn’t matter much for him. Well, it came back to bite him in the butt now, since what he didn’t realize is that not doing the homework for material he’d already mastered is an insult to the teacher who bothered to assign it (and even grade or review it), even though he probably did very well on exams in the class.
This will not fly in college. He won’t be able to just not do a problem set because he feels that he already has mastered the material. But of course, since problem sets are a big part of the grade in STEM classes, he’ll do them, I’m sure.
Under the circumstances, he should just be absolutely perfect in his STEM classes in first semester of senior year, be as charming and conscientious as possible, participate actively and eagerly, stop by after class to ask questions about the material, or about more advanced material related to what they’re doing in class, just everything he possibly can do to make the teachers adore him, and then ask them for a rec in mid fall.