It was in AP classes that I found other students like me - the ones who pretty much coasted along, never studying, only doing half the homework, etc, and still getting A's.

Not sure there were any PG kids in my HS, tbh. I would say of the twenty of us who all took all the AP classes for two years about 8 of us were "gifted", the rest worked and worked and worked for their grades. That's 8 kids out of a graduating class of 500, btw.
(I used quotes because, as far as I know, none of us had ever had an IQ test since probably early elm. At a certain point you just "know" when other people are on your wavelength or not.)