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.)