The problem is that these poor adults don't realize what they're missing. Maybe they know on some abstract level that education is good, but they don't value it

The problem is that these poor adults don't realize what they're missing. Maybe they know on some abstract level that education is good, but they don't value it where it counts - time, money, and effort. They get mad when they're expected to be involved with their children's education, ("It's your job to teach my kid - you're a teacher") they refuse to spend money on extracurricular activities, and they don't put forth the effort to actually make sure their kids are learning. What's more is that they are unwilling to pay the taxes that would pay for better public school education. Public schools in many areas are as minimalist as they can get. They teach only the required subjects; in many schools, home economics, auto repair, cooking, and budgeting are barely even electives. What's more is that the rich parents see these terrible schools and say, "Well, it's going to cost $10k a year to get my kid an education, but we need to pay it." Now the bad schools are filled exclusively with kids whose parents are indifferent to education. Not good.