He reminded me that children from a broken home are twice as likely to have behavioural problems, perform worse at school, become sexually active younger, suffer depression and turn to drugs, smoking and heavy drinking.
Almost half of cohabiting couples, compared to one in five married couples, have split by the birth of their first child.
This struck a chord. In my own school, less than half the children live with both parents; one third lives with a single parent; one in 20 with neither parent. Our daily experience, where the overwhelming majority of young people and parents are decent, hard-working and caring, is nonetheless marred by the behaviour of a poorly socialised minority, growing up without appropriate role models.
I also recall a remark from one adolescent, on hearing that her friend's mother was about to bring a new partner into the home: "Oh, he'll be great with you. He was the best dad I ever had."
The greatest single shift in my career is the massive increase in childhood mental illness. Adolescent clinical depression is now relatively common. At least some aspects seem rooted in family relationships.
Nor are family-based problems the preserve of the poor. The heartache, guilt and anxiety which family break-up engenders in children is as powerfully disturbing a factor among students in private schools as in the public sector.
Missing from Duncan Smith's thoughts was mention of the wider economic issues. Not simply poverty, but rampant consumerism. Our young people measure themselves, not by what they can do, but by what they can buy, by how they compare to the shallow role models of Hello and OK magazines, by access to the latest fashion accessory, whether Burberry or iPods.
Statements of regret for the demise of the family always imply a golden age where the family was universally better and different. Different perhaps.
My grandmother was illegitimate and raised in a one-parent family. My grandfather was born a week after his parents married. My great-grandfather was one of four children (by three different men) of a mother who never married and whose fourth child was fathered by the father of her first. She herself had been sexually abused by her father.
Promiscuity, illegitimacy and incest were all phenomena of that most ostensibly family-centred of ages - the Victorian years.
Nonetheless, nurture, unconditional affection, protection, constancy and love are essential if childhood growth and autonomy are to be achieved. It may be a flawed, imperfect tool to achieve these ends but the family is likely, on balance, the best one we have. We should protect it.
The "quiet man", as Duncan Smith once described himself to his party's conference, has at least half a point.
Alex Wood is headteacher of Wester Hailes Education Centre