When looking to supplement your high school classes with additional coursework, consider options such as local community colleges, reputable online programs, Stanford’s Pre-Collegiate Studies (SPCS), and Johns Hopkins’ Center for Talented Youth (CTY). The more rigorous the program, the better (assuming you can get good grades).
The harsh reality is that attending a prestigious high school (i.e., one that is a traditional feeder to the top colleges) carries a substantial amount of weight. If you are at an average high school, you’ll often need to work smarter and more creatively. Do this by going above and beyond your high school’s offerings. If your school only offers 6 AP classes, you’ll want to excel in all of them to be considered by a highly selective college (and ideally take some outside courses on the side). Show that you took advantage of everything your high school has to offer, and more.