You're basically suggesting that high school is to easy. I felt like hs was to easy too at the time. looking back I could've taken more AP's, but honestly, why would I have spent more time learning about things less useful to me when I had the option of learning about more useful things.
What I did was I just started bringing textbooks from any subject I was interested to all my classes and read them. If you are getting good grades no one will care. But really, unless your teacher is really awful they won't care anyway, because there are so many kids who do need help that they should be focusing on. Who gives a shit about the kid who probably could've passed the exam without taking the class when so many kids don't understand basic algebra, especially with no child left behind.
hs sucks, try to learn social skills by observing others and practice thinking about being in other peoples shoes to learn better empathy. Try to learn useful things like econ 101, programming, business stuff, math, etc.
Adolescence really just eats balls and there isn't much you can do about it.