But you simply can't rely on homework scores to be a proxy of learning or time spent studying anymore.
You never could. Parents do their kids' homework all the time, or siblings, or friends.
Homework used to be a measure for yourself to indicate whether or not you really understood the concepts being taught. Math is a prime example here. If you found your homework speed accelerating with confidence as you worked through problems correctly and accurately, it was a pretty good indicator of how you would perform on a test.**
It still is if you do it yourself and don't have ChatGPT do it for you. But it isn't a useful indication for parents or teachers, because the kids can just have ChatGPT do it for them, and moreover are encouraged to do so by the pressure to get good grades. By making the homework be graded only on adequate participation (which may be per-student) rather than on correctness, you shift the focus back to the homework being a way for students to get ready for the test and make it clear that having an AI do the work will prevent the teacher from knowing how well the student is doing, and will likely result in a lower grade on the test. Once the motivating factor of grades is eliminated and, in fact, reversed, they'll stop doing it, or will use it only to help them understand or to check their work, rather than using it as a crutch to actually do the work.
Ideally, teachers should give a large pile of optional homework.
For those students gifted with high motivation, they already recognize the value of optional homework that exists today. Any child gifted with high motivation wants to practice more, and is likely being raised by a parent who is more than capable of presenting those challenges. And does.
Any child gifted with high motivation and broad interests wants to practice stuff they already understand less so that they can do other things and learn other things. A child's time is a zero-sum game. The more time they spend doing things that are less useful, the less time they have for doing things that are more useful.
The ones who mindlessly work more problems because they are motivated to get good grades are the ones who aren't doing band, orchestra, chorus, or theater, who aren't going on field trips to learn about the world, who aren't getting the breadth of education that will prepare them for the real world, and will mostly end up in boring (but probably reasonably well-paying) jobs for the rest of their lives. They won't ever be the rockstar in their field, but they probably won't fail horribly. And I guess that's okay, but IMO it's not what we should try to inspire kids to become. The motivation should be to learn for learning's sake, and excess repetition is the opposite of that.
This is unfortunately no longer a valid measure because testing has become an exercise in psychological coddling. With time limits, bright lights, and the concept of failing, removed.
Meh. If that's your experience, then there's no hope for improving anything, because the kids who don't do well are going to pass anyway. This is how we end up with a bunch of graduates who can't actually do anything. I'm not saying you're wrong, but if you're right, then it's critical to fix that at the same time.