My humble opinion.
It depends a lot of on the teachers at the kid's high school. Therefore, enrolling in a competitive school which retains skilled and capable teachers may be beneficial in that respect.
On the other hand, for students who do not have good learning habits or solid foundations, it would be hard to dive into the AP world, with little help from the teacher and parents as life support.
It is not uncommon for teachers, even the good ones, to test concepts not covered in class or only gleaned over superficially in later tests. The teacher assumes that the students either learned the concepts before or studied the concepts after the lecture. Is it fair? No. But that is the reality in high school. A student has to put into extra work to get to the top. Not everything is fed by the teached in class.
