* How to close the achievement gap between privileged and poor students ?

The young teenagers who graduated from a special South Bronx middle school in 1999 became nationally famous. All black and Hispanic and largely from low-income families, the students had been recruited four years earlier to participate in an experimental programme called KIPP (ie, the Knowledge Is Power Program), designed to close the achievement gap between privileged and poor students. The experience seemed to pay off: in a citywide test, these students earned the highest scores of any school in the Bronx, and the fifth-highest in all of New York City. Most won admission to top high schools, often with full scholarships. They all seemed destined for college, and for successful, precedent-bucking, demographic-defying lives.

But six years after their high-school graduation, only about a fifth of KIPP’s first class had completed a four-year college degree. Most ended up dropping out, reaffirming America’s growing class divide on college campuses. KIPP’s founders were distraught, particularly because a college degree has never been more valuable, enabling Americans to earn some 80% more than people with only a high-school diploma. So how had KIPP failed to prepare these students for college? What did they do wrong?

Paul Tough, a journalist and former editor at the New York Times Magazine, aims to answer these thorny questions in “How Children Succeed”, an ambitious and elegantly written new book, now out in Britain. The problem, he writes, is that academic success is believed to be a product of cognitive skills—the kind of intelligence that gets measured in IQ tests. This view has spawned a vibrant market for brain-building baby toys, and an education-reform movement that sweats over test scores. But new research from a spate of economists, psychologists, neuroscientists and educators has found that the skills that see a student through college and beyond have less to do with smarts than with more ordinary personality traits, like an ability to stay focused and control impulses. The KIPP students who graduated from college were not the academic stars but the workhorses, the ones who plugged away at problems and resolved to do better.

So non-cognitive skills like persistence and curiosity are highly predictive of future success. But where do these traits come from? And how can they be developed? In search of answers, Mr Tough first looks at the problem on a neurological level. Apparently medical reasons explain why children who grow up in abusive or dysfunctional environments generally find it harder to concentrate, sit still and rebound from disappointments. The part of the brain most affected by early stress is the prefrontal cortex, which is critical for regulating thoughts and mediating behaviour. When this region is damaged—a common condition for children living amid the pressures of poverty—it is tougher to suppress unproductive instincts.

The science seems daunting, but it also points the way forward. Studies show that early nurturing from parents or caregivers helps combat the biochemical effects of stress. And educators can push better habits and self control. The “prefrontal cortex is more responsive to intervention than other parts of the brain,” writes Mr Tough. It stays malleable well into early adulthood. Character can be taught.

But schools have experience creating classes that raise test scores. Figuring out the best way to help youths develop “grit”—a passionate dedication to a goal—is trickier. Psychological interventions require more sophistication than teaching maths, and one of the big problems facing underperforming schools in America is a shortage of good teachers. But Mr Tough highlights some promising efforts to take these lessons about non-cognitive skills on board. A fascinating chapter considers the work of a young chess instructor in Brooklyn who turns unmotivated low-income students into chess champions by teaching them new ways to solve problems and recover from failures. In Chicago a programme called OneGoal, launched in 2009, is preparing struggling high-school students for college by stressing the link between hard work and destiny. And KIPP schools are now experimenting with something called a character report card, designed to show students that such traits can improve with time.

Replicating such initiatives on a grand scale will be hard, not least because they all seem to be run by uniquely talented and dedicated teachers and reformers. But at a time when ever more American children are living in poverty, better schools remain the most powerful anti-poverty tool available. After decades of failed efforts to improve the lives of poor students, Mr Tough has written a fine and provocative book about the kind of work that seems to be making a difference.