Every morning five-year-old Tristan starts his school day by reading in bed with his mother. He especially likes Enid Blyton. And even though he often doesn’t bother to get out of his pyjamas in time for his first class of the day, at the age of five he has a reading age of between seven and eight. He is also ahead of his peers in a variety of subjects—all, his mother reckons, thanks to home schooling.

Three decades ago home schooling was illegal in 30 states. It was considered a fringe phenomenon, pursued by cranks, and parents who tried it were often persecuted and sometimes jailed. Today it is legal everywhere, and is probably the fastest-growing form of education in America. According to a new book, “Home Schooling in America”, by Joseph Murphy, a professor at Vanderbilt University, in 1975 10,000-15,000 children were taught at home. Today around 2m are—about the same number as attend charter schools.

Although home schooling started on the counter-cultural left, the conservative right has done most to promote it, abandoning public schools for being too secular and providing no moral framework. Today the ranks of home-schoolers are overwhelmingly Christian, and 78% of parents attend church frequently. According to the National Household Education Survey in 2007, the main motivation for home schooling was for religious or moral instruction (36%), followed by school environment (21%) and the quality of instruction available (17%). After this comes concerns about special education, the distance of travel and even nut allergies.

Home schooling is not exclusively white and Christian. In 2007 a report found that Muslim children were one of the fastest-growing groups; black-home schoolers are around 4% of the total and comprised 61,000 children. The super-wealthy, and parents who must move around a lot, are also taking up home schooling in increasing numbers because of its flexibility.

According to Mr Murphy’s book, parents want to control not only what their children learn, but the values they pick up and the company they keep. They are also increasingly convinced that schools are not that good at teaching. Academically, home-schooled children seem to do well; they enter higher education in proportions similar to those who are conventionally educated, and score as well or better on college entrance exams. Nor, on the evidence of Mr Murphy’s book, are they socially backward: most seem confident, assured and well-adjusted. They also have fewer behavioural problems. But one study did find higher attrition rates when they enter the armed forces.

State laws vary widely in how much regulation they impose on home-schoolers and how much accountability they require. Pennsylvania, California and New York are stricter than most, but parents are not deterred. Mr Murphy says the movement is all part of the breakdown of American schooling from public monopoly; home schooling, he says, “is the most radical form of privatisation”. Public schools can do little but co-operate these days, and most offer access to school facilities, websites, books and other materials. Some even allow home-schoolers to take specialist courses—allowing the school to tap into a portion of public financing they would otherwise lose entirely. Home schooling still has its enemies, but pragmatism is becoming the order of the day.