As a new school year begins, more than 50,000 Australian children will be home-schooled and in most cases, their parents are doing it illegally.

It is compulsory to send children between the ages of six and 16 to school, or register them for home schooling, but more parents are opting out of the traditional school system and keeping their children at home.

However, thousands of parents across the country are not registered and that means they potentially face prosecution.

Governments have been reluctant to take legal action, but in a landmark case last October, Bob Osmak from the Home Schooling Association of Queensland was prosecuted for not registering with the Home Education Unit to home school his 13-year-old daughter.

Mr Osmak had home-schooled his nine children.

He was charged under the Queensland Education Act that says parents have to enrol children of compulsory school age in a school, or register them for home schooling.

Mr Osmak was found guilty and fined $300 plus costs.

"I didn't register with the Home Education Unit. I refused to do that because I see education as something of a parental right," he said.

"We as parents know and love our children best. It's not some cold faceless bureaucrat in the education department that knows what's best for your child.

"Many home-schooling families kind of do it secretly because they fear Education Queensland taking legal steps against them and so forth, sending police to the door and that kind of thing."

Underground education

There are 942 children registered with the Home Schooling Unit this year, but Mr Osmak believes there may be another 10,000 home schooling underground in Queensland.

During the past decade the home-schooling community has boomed, thanks to the internet and the availability of how-to-do-it kits and mail-order curricula.

At a get-together of home schoolers in a suburban park in Brisbane, one mother, Cindy, said she was about to start home schooling her son but was afraid of the paperwork involved.

"I'm not planning (on registering) because of the work involved," she said.

"I'm not very organised and disciplined in that sense so that would be a big thing for me to undertake."

Cindy is one of a large number of underground home schoolers but the secrecy and distrust has made it difficult for researchers to get hard data on whether home schooling produces a better or worse education.

"There is this sense of distrust; this general sense that 'the Government doesn't tell us what we need to know. It's like they don't want us to exist'," said Glenda Jackson, who did her PhD on home schooling at Monash University.

"We can't find the families to do a population sample testing that's even, and when you interview, when you're doing research with these parents, they can be very suspicious about who you are and why you're doing the research."

Why home school?

The Tasmanian Home Education Advisory Council recently asked its 600 registered parents why they decided to home school in the first place.

Seventeen per cent said the main reason was religion, nearly half listed philosophical reasons, while 27 per cent were not happy with the local school and 7 per cent had children with special needs.

Education Queensland did a similar voluntary survey in 2002 and found 20 per cent of parents listed religion as the main reason for home schooling and 21 per cent said it was because they were not happy with the local school.

In the United States, Stanford University sociologist Rob Reich said that underlying those reasons was often a deep distrust of authority.

"I know plenty of home-schoolers who would still home school even if they had an exceptional public school right next door to them," said Mr Reich.

"They're simply opposed in principle to state authority over their children, which they extend not only to a school environment, but even to state hospitals or regulations of another sort."

The challenge now for education departments around Australia is to get home-schooling parents to agree to some form of monitoring of their children's education.

"Standards exist for a reason and they're about the kids not about the parents and their ideas about what they should do," said the acting manager of the Queensland Home Education Unit, Hanne Worsoe.

"That's why we live in a civil society that provides that capacity to represent children and to monitor their educational needs. If people aren't registered I'd say you're breaking the law, and if you're doing the right thing by your kids you've got nothing to hide."

- Listen to Ian Townsend's full story, Opting Out and Staying Home, on Background Briefing, ABC Radio National.