It's probably best going forward to grade only in-person proctored exams using paper, or offline air gapped computers in the case of programming courses.
The most practical solution I know is the teacher asks you questions about your code in person to make sure your understand it. Even better when they come up with a small change and you have to implement it on the spot, or at least explain exactly how you would do it if there's not enough time.
It catches lazy vibe coders who don't even read the code but lets through those who only use AI to save time. That's exactly what you need if you want your students to learn.
For CS, homework should be done how you want. Homework is practice. Let AI assist you, but you better learn it because you'll be coding some part of it in lab with a physical programming book as a reference. They can lock down computers for labs to prevent web access or limit only to certain websites. Since labs are weekly, it will be obvious if someone is not learning as they do the homework. It won't be an F on the final as the first sign of trouble.
Schools can do things to improve student resources. Self host llms that are not corporate controlled that every student can use. The school can provide a search engine that is useful and not google's marketing. You can offer an education proxy that caches the pages you look at when doing education work, preserving anything you cite. This can all feed into the school llms for rebuilding to keep them trained on current info.
Also, I never had a computer science class where exams were administered on a computer. I only graduated like 10 years ago, too. I shit you not, even my x86 assembly class was all pen and paper too, and yes, we were graded for code accuracy.