The problem isn't that AI detection doesn't work. State of the art in this field is pretty solid. The only issue is that it's probabilistic, so it sometimes fails, and when it does, we have nothing else in situations where you actually want to know if someone put in the work.
So what are you proposing, exactly? That we run a large-scale experiment of "let's see what happens if children don't actually need to learn to do thinking and writing on their own"? The reality is that without some form of compulsion, most kids would rather play video games / scroll through TikTok all day. Or that we move to a vastly more resource-intensive model where every kid is given personalized instruction and watched 1:1?