[amateurpolymath]

I can't speak for other states, but in Florida it's very easy to do dual enrollment, possibly the best option for a gifted high school student. As long as your courses are at a public university or community college, your tuition is fully funded by the state. Your high school credits are satisfied by college courses, you get college credits that are easily transferred to other universities when you graduate, for free.

There are also plenty of challenging classes for gifted students, but this might vary from school to school.