Over the past generation, members of the college-educated class have become amazingly good at making sure their children retain their privileged status. They have also become devastatingly good at making sure the children of other classes have limited chances to join their ranks.

How they have managed to do the first task - giving their own children a leg-up - is pretty obvious. It's the pediacracy, stupid.

Over the past few decades, upper-middle-class Americans have embraced behaviour codes that put cultivating successful children at the centre of life. As soon as they get money, they turn it into investments in their children.

Upper-middle-class mothers have the means and the maternity leave to breastfeed their babies at much higher rates than high-school-educated mothers, and for much longer periods.

Upper-middle-class parents have the means to spend two to three times more time with their pre-school children than less affluent parents. Since 1996, education expenditures among the affluent have increased by almost 300 per cent, while education spending among every other group is basically flat.

As life has got worse for the rest in the middle class, upper-middle-class parents have become fanatical about making sure their children never sink back to those levels. Of course, there is nothing wrong in devoting yourself to your own progeny.

It is when we turn to the next task - excluding other people's children from the same opportunities - that things become morally dicey.

Dr Richard Reeves of the Brookings Institution recently published a book called Dream Hoarders, detailing some of the structural ways the well-educated rig the system.

The most important is residential zoning restrictions. Well-educated people tend to live in places like Portland, New York and San Francisco that have housing and construction rules that keep the poor and less educated away from places with good schools and good job opportunities.

These rules have a devastating effect on economic growth nationwide. Research by economists Hsieh Chang-tai and Enrico Moretti suggests that zoning restrictions in the nation's 220 top metro areas lowered aggregate United States growth by more than 50 per cent from 1964 to 2009.

The restrictions also have a crucial role in widening inequality.

An analysis by economist Jonathan Rothwell finds that if the most restrictive cities became like the least restrictive, the inequality between different neighbourhoods would be cut in half.

Dr Reeves' second structural barrier is the college admissions game. Educated parents live in neighbourhoods with the best teachers, they top off their local public school budgets and they benefit from legacy admissions rules, from admissions criteria that reward children who grow up with lots of enriching travel and from unpaid internships that lead to jobs.

It is no wonder that 70 per cent of the students in the nation's 200 most competitive schools come from the top quarter of the income distribution. With their admissions criteria, America's elite colleges sit atop gigantic mountains of privilege, and then with their scholarship policies they salve their conscience by offering teeny stepladders for everybody else.

I was braced by Dr Reeves' book, but after speaking with him a few times about it, I have come to think the structural barriers he emphasises are less important than the informal social barriers that segregate the lower 80 per cent.

Recently, I took a friend with only a high school degree to lunch. Insensitively, I led her into a gourmet sandwich shop. Suddenly I saw her face freeze up as she was confronted with sandwiches named "Padrino" and "Pomodoro" and ingredients like soppressata, capicollo and a striata baguette.

I quickly asked her if she wanted to go somewhere else and she anxiously nodded yes, and we ate Mexican.

American upper-middle-class culture (where the opportunities are) is now laced with cultural signifiers that are completely illegible unless you happen to have grown up in this class. They play on the normal human fear of humiliation and exclusion.

Their chief message is, "You are not welcome here." In her thorough book The Sum Of Small Things, Professor Elizabeth Currid-Halkett argues that the educated class establishes class barriers not through material consumption and wealth display but by establishing practices that can be accessed only by those who possess rarefied information. To feel at home in opportunity-rich areas, you have got to understand the right barre techniques, sport the right baby carrier, have the right podcast, food truck, tea, wine and Pilates tastes, not to mention possess the right attitudes about writer David Foster Wallace, child-rearing, gender norms and intersectionality.

The educated class has built an ever more intricate net to cradle us in and ease everyone else out.

It is not really the prices that ensure 80 per cent of your co-shoppers at Whole Foods are, comfortingly, also college graduates. It is the cultural codes.

Status rules are partly about collusion, about attracting educated people to your circle, tightening the bonds between you and erecting shields against everybody else. We in the educated class have created barriers to mobility that are more devastating for being invisible.

The rest of America can't name them, can't understand them. They just know they are there.

NYTIMES