As life has gotten 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, and of course there’s nothing wrong in devoting yourself to your own progeny.

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