I’m sure you know more about boarding school than I do, but this is what I’ve also heard from my hyper-competitive math friends at the school. I’m sure that what you’re saying is objectively correct, top performing competitive STEM students may (unfairly and unjustly) perceive the student body in a very skewed way.
Btw, this is not my real name. I just use it as a pseudonym sometimes.
All 3 are amazing for STEM - we say this based on a lot of feedback we have from college admissions officers, and parents with kids at all 3 schools.
Many people on this board know that PA and PEA have relatively high homework loads, and at times some (certainly not all) kids complain about the intensity and stress. But we also hear a lot about the high intensity of the student body, and the parents, at Harker. It’s a high achieving private school in Silicon Valley with a STEM bent, so this should not be a surprise.
Given the fun ECs at PA and PEA, and not having to deal with a daily commute, I would guess they are no more intense than Harker, and probably less so given the many attributes of residential boarding.