[andrepd]

> None of the colleges I applied to asked for my family's tax history or income level, except for on the separate financial aid application.

Obviously that's not the point, as I'm sure you understand. It's that children lower-income families tend to have a harder time succeeding in school or participating in extracurriculars (maybe they don't have transportation, maybe they need to help with chores and cooking because parents work two jobs, maybe they don't have educated parents with free time to help with homework, etc etc etc), while higher-income families can afford all the help. Note that of course the same problem applies in myriad other situations: children in unstable households, with parents victim of domestic violence, with parents with mental health or drug addiction issues, etc.

This (correlation between parent's income and educational success) is both intuitively clear and also amply documented.