I agree with those saying you can’t/shouldn’t forbid it. As someone in computer science, the important thing to me is to make sure they understand what those LLMs are and aren’t. Specifically, the ‘M’ in “LLM” is for “model” - they’re a detailed model of what a conversation should look like, especially what a response to a question should look like. But looking right is different from being correct. You can ask one for a mathematical proof and it will give you one that looks right, but it probably won’t be.
The other thing I’d try to get them to understand is that the leaning part of school is much more important than the grade part, especially if they’re going to go on to college. They could use an LLM to help them create a term paper, but if they didn’t learn anything it’s going to catch up to them and cause problems down the road.