It’s really simple. Smarter parents take their kids out of public school and homeschool.
Not necessarily. My kids have to public school from kindergarten. My oldest son goes to a high school in a lesser desirable neighborhood because they have an IB program. He scored a 1330 on his first SAT attempt and a 31 on his ACT with no prep class. It’s just that we are involved parents and he is a motivated student.