As other mentioned you do compete with the opportunities available to you in your own school and your performance is evaluated relative to your peers. Our kids attend a top public in an affluent area of LA and we have every AP class under the sun. Counselors are very accommodating with DE as well, so 4.8+ weighted UC GPAs are pretty common around these parts.
But despite the AP/DE buffet and high GPAs, our school never beats the published acceptance rate at UCLA and only get about 27-29 out of 300+. So while a 4.7/12APs is great, in context here its only above average.
You can see the results by HS here.
There was an interesting discussion on this topic a few years back here on CC.