> I've tried to explain to my students that it's in their interest to think about home assignments on their own, but the majority will obviously use gen AI, and it's such a waste of time to check and grade LLM output.

I think the problem is the students also take ~4-5 subjects per semester, and each of them may be just as demanding. High school is even more spread out with 6-8 subjects per semester. There's only a certain number of hours during the day for study and homework. For many, math homework ends up being the most time-intensive. Also these exams determine their GPA which in turn plays in part in determining their standing for the next few decades of their lives.