Very high rates of family breakdown in the United States are subtracting from what very large numbers of students are learning in school -- besides holding them back in many other ways.

This in turn is damaging the country economically, by making us less hospitable to innovation while also leaving millions of Americans less competitive in an increasingly demanding worldwide marketplace.

All of which is leading -- and can only lead -- to deepening class divisions.

Family fragmentation (which has eclipsed "family breakdown" as the preferred term of art) is certainly not the only cause of diminished social and economic mobility. But it's a critically important and, too often, downplayed one.

The scale of the problem is immense.

• In one study cited by Andrew Cherlin of Johns Hopkins University, by age 30, one-third of American women had spent time as lone mothers; comparable proportions in France, Sweden and the western part of Germany were half as large or even less.

• Nationwide, about 40 percent of all American children (about 30 percent of white babies) are born outside of marriage. And while divorce rates have dropped slightly since the 1980s, it's still estimated that slightly more than 40 percent of all first marriages fall apart, with the rate around 50 percent for subsequent marriages.

In Hennepin County, in 2009, 61.5 percent of Hispanic babies, 84.3 percent of the children of U.S.-born African-Americans and 88.8 percent of American Indian babies came into this life out of wedlock. (That compares with 18.3 percent for whites and 35 percent overall.)

The consequences, meanwhile, are clear -- and discouraging.

The Census Bureau reports that white families headed by single mothers are more than three times as likely to be poor as black married-couple families (25.2 percent vs. 7.9 percent).

Suffice it to say that research evidence is overwhelming that single parenthood depresses academic performance, along with every other conceivable measure of well-being.

Or, as framed famously by sociologist David Popenoe: "I know of few other bodies of data in which the weight of evidence is so decisively on one side of the issue."

Many observers, when commenting on growing income inequality in America, focus correctly on evidence that, around the world, well-educated men and women enjoy increasing advantages over poorly educated ones.

Yet for some reason less attention is almost always devoted to the pivotal connection between family structure and success in school and in the economy.

Rarely, in short, is sufficient attention paid to how family fragmentation -- in which, unhappily, the United States leads the industrialized world -- is contributing to widening disparities of income and wealth.

Many liberals seem too busy instinctively blaming conservative ideas and policies for those troubling disparities, while many conservatives, equally unhelpfully, think it adequate, whenever the subject comes up, to charge liberals with suffering "class envy" and waging "class warfare."

Might I respectfully add here that it is impossible for me to imagine how liberal friends could not be at least as concerned as I am from the conservative side of the aisle about the thinning of marriage and its straight line to social class ruptures?

How might all this play out in Minnesota over the next two or three decades? Let me suggest a few possibilities, none of which is attractive.

Ironically, worsening family fragmentation is something the nation's often disparate groups share. High nonmarital birth rates and divorce rates are far from exclusively a low-income or minority phenomenon. They increasingly characterize the great American middle.

Brad Wilcox and Elizabeth Marquardt of the National Marriage Project wrote late last year of how family fragmentation has come to be a powerful force among Americans they describe as "moderately educated" -- a full 58 percent of adults who have graduated from high school but who don't have four-year college degrees.

Back in the 1970s, Wilcox and Marquardt noted, the moderately educated were just as likely to be married as highly educated Americans.

Today their likelihood of being married -- which is to say, the chances of their having children inside rather than outside marriage -- more closely resembles that of the least educated among us.

With great numbers of average Americans increasingly resembling those on lower economic rungs, various gaps between "haves" and "have-nots" may come to be less ethnically or racially contoured than they have been. That's the potentially good news.

Definitely not good news will be increasing social space and differences -- including different levels of frustration and anger -- between those Americans who are well-prepared for an ever more demanding economic future and those who, along with their sons and daughters, are not.

More fragile family structures, meanwhile, guarantee that educational achievement in Minnesota and the United States will remain weaker than international competition compels, with serious economic prices to be paid.

Many kids always will do great regardless of their circumstances at home, and many single parents always will be heroic. But poor odds of success will constrain many millions, not least many children of color, to whom the term "achievement gap" has come to be nearly soldered.

Simply put, so long as fragmentation rates remain as huge as they are, enormous numbers of children will keep doing inadequately in school (and, as a result, in economic life) -- no matter how much money we spend, no matter how boldly politicians lead and no matter how passionately teachers teach.

Discontent inescapably will grow. Americans may continue to feel ever less affinity for "neighbors" who really don't live in the same vicinity -- or, in many ways, in the same society. And many may demand more of government to help them get by.

Yet, obviously, this is exactly the wrong era to imagine taxpayers having the inclination, or governments having the wherewithal, to deliver additional income support or other benefits.

The collapse of marriage in many quarters of our state and country is not the only factor at work in the thickening of barriers between the better-off and the rest. But it's undeniable that ties between strong marriages among grown-ups and strong futures for their children can be potent.

So, how to strengthen marriage? No known roster of recommendations is adequate, but here's one idea that focuses on the boys who become the men whom women frequently and understandably are not interested in marrying.

Harvard political scientist Paul Peterson has written that the "biggest impact" of a private educational experience for minority children comes in later years -- and has to do with keeping them in an educational environment that "sustains them through graduation."

Without getting too metaphoric, let's stick with the idea of "sustaining."

It's hard to conceive of hurts much deeper than what have been called "father wounds" -- as well as other family absences, very much including missing mothers.

For many boys (and girls) suffering those pains, I would argue, the most sustaining type of education, providing sustenance of the most personal and vital kind, is found in the type of school led by a nun I once met.

I asked this principal of a Catholic elementary school in the Twin Cities what her institution's mission was. "To manifest God's love in every child," she said, or words close to that. As educational mission statements go, this was one of the briefest yet meatiest ever drafted.

Might some proportion of boys who might otherwise drown be rescued in schools like this? And might the risk diminish for their becoming adults, in sociologist William Julius Wilson's iconically sad term, "unmarriageable men"? I would think so.

There are plenty of good reasons why all children deserve opportunities for the kind of education made possible (be prepared) by real school choice and vouchers. This is just one more.

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Mitch Pearlstein is founder and president of the Center of the American Experiment. His new book is "From Family Collapse to America's Decline," released by Rowman & Littlefield.