^ The problem is that the “standard” math curriculum skips a large portion of mathematics, and doesn’t teach what is covered in very much depth (and teaches it in an extremely boring way that tends to kill interest in real mathematics, which is beautiful and intriguing and fun). Kids who find the curriculum too easy and who are bored most often choose to “accelerate”, which just means moving ahead to do portions of the curriculum at an earlier age and skipping other portions, which results in more math missed, and does not provide more depth. AoPS founder Richard Ruszcyk refers to this as the “Calculus Trap”:
https://artofproblemsolving.com/articles/calculus-trap
See also:
https://artofproblemsolving.com/articles/discrete-math
The urge to get to the AP level only compounds this. The trick is to find ways to deepen understanding and enjoyment of math, not to skip over fundamentals in order to get to a more “advanced” portion of the curriculum taught at a superficial level sooner. There are useful programs and resources to do this; a few school systems provide support for these kind of things, but for the most part it’s something that motivated and talented kids have to pursue on their own.