[Yoric]

Or perhaps they have more time to spend with children, because they don't need to work three jobs, or failing that, can afford to have someone else spend time with their children.

Also, yes, there is a tie between income, education and culture, and it goes both ways. Starting one's life around cultured and educated people does help you grow into someone who has access to a better job, which gives you access to better education and culture, etc.