EXPENDABLE: Poor boys are falling behind poor girls, and it’s deeply troubling.

It’s become a fact of American life that girls are better than boys at school. They get better grades. They’re suspended less. For every generation since the boomers, women have been more likely than men to earn high school and college diplomas.

In fact, girls are pretty much the only reason the high school graduation rate went up in past 40 years, according to calculations by Harvard economist Richard Murnane. The male high school graduation rate has been stuck at 81 percent since the 1970s, while the female graduation rose from 81 percent to 87 percent.

Women have been so persistently superior it is perhaps time for a new stereotype about the sexes — girls as bookish mavens like Lisa Simpson; boys as goof-offs like Bart.

Yeah, that’s not a new stereotype. And negative stereotypes about boys — which abound, especially among the overwhelmingly female teacher corps — are probably one of the reasons for this.

Which 2016 Presidential candidate will support legislation to protect boys in the classroom?

But it’s also true that the revolution in family affairs — that is, the rise of single-parent families — has indeed hurt boys worse than girls. (You can read this study, or you can listen to hiphop, in support of that). The study, though, seems to think that single-parent families are caused by “income inequality,” when it’s more likely that things are the other way around.