The Economist:

THE first thing you notice about Karen Allen’s house is that it is spotless. Even in her teenage boys’ bedrooms, not a thing is out of place. And her boys, Thomas and Taylor, are polite and engaging. Your correspondent found himself being grilled about his travels by a boy who had clearly Googled him. In this household, every chance to learn something new is eagerly seized, explains Mrs Allen.
The Allens are home-schoolers. Instead of sending their children to a public (non-fee-paying) or private school, they teach them at home. They are far from alone. A generation ago, home-schooling was rare and, in many states, illegal. Now, according to the Department of Education, there are roughly 1.5m home-schooled students in America, a number that has doubled in a decade. That is about 3% of the school-age population. The National Home Education Research Institute puts the number even higher, at between 1.8m and 2.5m.
Why do people teach their children at home? Many of the earliest were hippies who thought public schools repressive and ungroovy. Now they are far more likely to be religious conservatives. At a public school, says Mrs Allen, her boys would get neither much individual attention nor any Christian instruction. At home they get plenty of both.
In a 2007 survey by the Department of Education, 88% of home-schooling parents said that their local public schools were unsafe, drug-ridden or unwholesome in some way. Some 73% complained of shoddy academic standards. And 83% said they wanted to instil religious or moral values in their children–a number that has risen from 72% in 2003.

I think the article overplays the religious angle.