They're intertwined. Many things in life you can't learn from textbooks, which you can from having friends who have parents who are doctors and lawyers and business owners. When they cluster together, by living near each other in higher priced homes and towns, and send all their kids to similar schools, you end up with an unequal education for the kids because while the teachers and the books can be the same, the learning environment as well as access to adults with better resources can't be made the same.