Taking the AP exam in high school is just a tactic. A situation like:
Student: Man I don't want to take this boring mandatory calculus class.
Teacher: You have to.
Student: But I already know all this stuff!
Teacher: Mmmmm, well that's just like your opinion, man.
Student: What if I ace the AP exam?
Teacher: OK, then I would believe you.
In my experience it's pretty rare for all of high school to be boring. You probably haven't read the particular works they're discussing in English class, you probably haven't read about the particular time period they're discussing in history. And even if you have, there's plenty more you can learn about those things. The most common area to be bored by is math, because you can pick that all up yourself relatively easily.
I suppose it depends on when this all kicks in. In my case, in kindergarden I was tested into 11th grade; in response I was placed into 1st grade. Which was fine, honestly, I spent a lot of time drawing and so forth, but things got really unpleasant and pointless in 7th grade, so I dropped out, and dropped into college. I'm reading a lot of people complaining about the damage to one's social prospects, and surprisingly few calling out what I experienced: school was minimally useful, the social environment was pretty toxic, and in my case, the teacher was tyrannical.
University was so much better! For highly motivated and gifted students, early university can be a great option. It is important to place it on a larger arc of one's own journey of learning, development, and self discovery, however, that must continue for as long as one keeps growing.
As an important aside, girls and boys have approximately equal interests in science math and technology earlier on; for girls this changes pretty severely in middle school and high school. I'm sure there a very large social component to this, parents would do well to inoculate against it by finding alternative environments, and university is certainly one.
Student: Man I don't want to take this boring mandatory calculus class.
Teacher: You have to.
Student: But I already know all this stuff!
Teacher: Mmmmm, well that's just like your opinion, man.
Student: What if I ace the AP exam?
Teacher: OK, then I would believe you.
In my experience it's pretty rare for all of high school to be boring. You probably haven't read the particular works they're discussing in English class, you probably haven't read about the particular time period they're discussing in history. And even if you have, there's plenty more you can learn about those things. The most common area to be bored by is math, because you can pick that all up yourself relatively easily.