In my experience rubbing shoulders in these circles, kids going to the top tier prep schools are often just really impressive--the culture at these schools normalizes an expectation of high achievement across multiple domains. Not uncommon to see the same kid be a starting quarterback on the football team, an award winning painter, and a nationally ranked debater. I got into an Ivy equivalent college by enthusiastically pursuing my interests at a less competitive high school, and frankly, I think I might have cracked under the pressure at one of these top tier prep schools.

I completely believe that there are many majors/programs at Harvard no more rigorous/educational than those at decent large state universities, but make no mistake, these top tier prep schools are often leaps and bounds more difficult/rigorous than well ranked suburban public high schools, outside of the nationally exceptional magnets like Thomas Jefferson or Bronx Science.