What a child wants to do is what a child wants to do right now. If you ask the same question a few minutes later, you could get an entirely different answer.
As adults who have lived through being children, a surprising percentage of us actually do know better than a small child what's best for the small child for a surprising percentage of their lives.
I read once about a highschool boy, a good student, who was shocked when a teacher asked him "What do YOU want to do?". What? he thought. This question has never crossed my mind. Nobody told me I can make my own mind. It was always "teacher knows best" and "parent knows best" and "be a good student and learn what we teach you, do what we tell you".
I wrote from this point of view, but I agree that parents and teachers know better most of the time, I just don't know if it is good to try so hard to make sure the child doesn't make any "wrong" choices.
As adults who have lived through being children, a surprising percentage of us actually do know better than a small child what's best for the small child for a surprising percentage of their lives.