Just look at who runs the government at the highest levels—elected, and appointees, both. Heavy representation of Ivies and other elite schools... sure, OK, not surprising, but you look farther back and more often than not, yep, expensive prep school, rich-parish catholic private schools, or (less commonly) a well-into-the-top-1% public high school (usually with selective admission—basically by definition, since you can't realistically do that well, as a school, without it). Notably, the latter option is simply absent if you don't live in the right places, which tend to be rich, expensive ones, near or in a handful of major cities.

If you're in a normal-ass public school—even a good, but not exceptionally good selective-admission one—when you're 16 because your parents couldn't afford the straight-up costs, or relocation & other maneuvers (e.g. résumé padding), to get you into a top secondary school, let alone university—many doors of possibility in your life have already begun to swing shut, whether you realize it or not. It's not impossible you'll get into those kinds of positions despite that, but... your odds are even worse than one might suppose, had one not noticed this tendency.

(of course, it's worse still for certain other pursuits—for some sports and musical instruments, if you're not already damn serious about it and receiving excellent [$$$] coaching/instruction by age 8 or so, then that's already effectively cut off for you as a possible future career. Decide at 14 that's your passion and give it your all? Too bad, you're already too far behind, learn to enjoy participating as a hobby on weekends.)