The most important divide in America today is class, not race, and the place where it matters most is in the home．Conservatives have been banging on about family breakdown for decades．Now one of the nation's most prominent liberal scholars has joined the chorus. 
    Robert Putnam is a former dean of Harvard's Kennedy School of Government and the author of Bowling Alone (2000), an influential work that lamented the decline of social capital in America, In his new book, Our Kids, he describes the growing gulf between how the rich and the poor raise their children．Among the educated elite the traditional family is thriving : fewer than 10% of births to female college graduates are outside marriage--a figure that is barely higher than it was in 1970．In 2007 among women with just a high-school education, by contrast, 65% of births were non-marital．Race makes a difference : only 2% of births to white college graduates are out-of-wedlock, compared with 80% among African-Americans with no more than a high-school education, but neither of these figures has changed much since the 1970s．However, the non-marital birth proportion among high-school-educated whites has quadrupled, to 50% , and the same figure for college-educated blacks has fallen by a third, to 25%．Thus the class divide is growing even as the racial gap is shrinking. 
    Upbringing affects opportunity.Upper-middle-class homes are not only richer(with two professional incomes ) and more stable; they are also more nurturing．In the 1970s, there were practically no class differences in the amount of time that parents spent talking, reading and playing with toddlers．Now the children of college-educated parents receive 50% more of what Mr．Putnam calls "Goodnight Moon" time (after a popular book for infants). 
    Working-class parents, who have less spare capacity, are more likely to demand that their kids simply obey them．In the short run this saves time; in the long run it prevents the kids from learning to organize their own lives or think for themselves．Poor parenting is thus a barrier to social mobility, and is becoming more so as the world grows more complex and the rewards for superior cognitive skills increase. 
    Stunningly, Mr．Putnam finds that family background is a better predictor of whether or not a child will graduate from university than 8th-gmde test scores．Kids in the richest quarter with low test scores are as likely to make it through college as kids in the poorest quarter with high scores. 
Mr．Putnam suggests a grab-bag of policies to help poor kids reach their potential, such as raising subsidies for poor families, teaching them better parenting skills, improving nursery care and making after-school baseball clubs free．He urges all 50 states to experiment to find out what works．A problem this complex has no simple solution.