1 Doctors are marrying doctors. Lawyers are marrying managers. Professors are marrying politicians. They then all have kids. The kids are surrounded by their parents friends and learn how to have interesting conversations with them. Learn that sometimes even experts are wrong. The kids then go to university with a 529 and are able to excel and form connections because they are not afraid to talk or argue with the professors and to do networking. The middle-class kids who diligently turn in all of their work on time and take the messages of their teachers as the word of God get left compleatly behind.
2 This cycle is intensifying and is creating a new class. It used to be the case that the doctor would marry a nurse and the lawyer would marry a secretary (would marry people that didn't have a comparable income or status). But when women were forced into the economic system in the 20th century (when it was figured out that they had a comparable IQ that could be exploited) men then had the option of picking a partner that brought money to the table.
3 Professionals having kids with other professionals. The kids then growing up themselves to become professionals. Marrying other professionals to have kids of their own. Households combine and lineages are born. The process will probably not stop unless the meritocracy is abolished or until professionals stop inbreeding with each other.