The implication of OP’s statement is that the quality of principals, counselors, and teachers doesn’t matter. This is absolutely not true.

People seem to comparing UC/UMC public schools with schools suffering from poverty. There is no question that the kids in their two schools will have vastly different outcomes regardless of what the school is like. But if you’re just comparing schools on opposite sides of the bell curve, you’re leaving out millions of schools. Take a school where 65% of the student body comes from families who heavily value education, and compare that to a school where 45% of families heavily value education. If the first school has a terrible principal and the second school has a good principal, teachers, etc., I don’t think you can immediately conclude which one is going to produce the best student outcomes.

Also, before someone waxes poetic about the noble poor and the mean rich, there are plenty of poor immigrant parents who raise the local school test scores, which is why the FARMs rate is a less reliable indicator of test scores than the demographics of the neighborhood.