In fact, Boeckenstedt’s chart shows an almost perfect correlation between institutional selectivity and students’ average family income, a steady, unwavering diagonal line slicing through the graph. With only a few exceptions, every American college follows the same pattern.

SAT scores of children, like IQ, are positively correlated to parental income. If you take two children, one from a family with income of $50K and another from a family with income of $200K, maybe there is only a 55-60% chance that the child from the richer family has a higher SAT score. But if you randomly select 1000 children each from families across the country with incomes of $45K-$55K and $180K-$220K, the average SAT score and IQ of the children from the richer families will almost always be higher. Since colleges enroll thousands of students, one should expect that higher-SAT schools have students from richer families.