Was this El Camino High School in Oceanside, CA by chance? I came here to say something basically identical - but realized you stole my thunder, since your son had a near identical experience. :)
All the smartest kids in my high school (including 1500+ SAT types) all went to UCSD/UCLA/Berekly. It wasn't until I was in grad school years later, and hung around lots of Stanford/Harvard/MIT grads that I realized they weren't really much smarter or harder working than all the kids in my high school, they just grew up with the expectation of going to a Ivy school ingrained in their experience.
It was Grossmont High School on the border between La Mesa and El Cajon, CA. It was the same with my son. He hung out with a group that included all the 10 best students by GPA in his class. Except for him, they all went to state schools.
All the smartest kids in my high school (including 1500+ SAT types) all went to UCSD/UCLA/Berekly. It wasn't until I was in grad school years later, and hung around lots of Stanford/Harvard/MIT grads that I realized they weren't really much smarter or harder working than all the kids in my high school, they just grew up with the expectation of going to a Ivy school ingrained in their experience.