Four years of sports together either high GPA won't do a thing for an Asian kid at El Toro HS vs at an IUSD HS.
I think what he/she means to say is that a high-achieving Asian HS student in another school district with a well-rounded CV is likely to stand out more to a college admissions committee than a similar HS student with the same credentials who graduated in IUSD.
Sad to say this but I get the feeling that this is true. Having been on the other side, both medical school and residency admission committees tend to have a bias towards diversification once an arbitrary threshold is met for interviewing/accepting a certain amount of applicants from the same school/program. Interestingly, this logic doesn’t apply to certain schools if they have prestige behind their name.
IUSD will do ok in getting over the UC threshold.
Further than that (eg, Stanford, Ivy, MIT), it’s anyone’s guess.
Side note: look up AMCAS GPA matriculant data and stratify the data by race. On average, Asians would need a higher GPA to be accepted vs other cohorts.