In other words, the cost of non-government education could well be the single largest expenditure category for a family after housing. At least buying a house is usually a good investment. And while education is also certainly an investment, spending such a large amount of money on it hardly looks like a prudent decision when the government offers something just as good for nothing.

But parents freely choose to reject government schools, and the proportion who do so has been growing since 1977, when only 21.1 per cent of children were in non-government education. Since then, the proportion in non-government schools has grown every year until 2013 when it stabilised at 34.9 per cent.

Why is it that Australians, who see themselves as egalitarian piss takers, embrace private education far more than other countries?

Not just a search for results

My guess is they are not doing it solely in the hope of better academic results. For those at the most expensive schools, it's often family tradition or a desire to build networks for their children. And I suspect many view it is offering their children what they see as a better environment for developing such intangibles as "character" and mixing with peers who they hope will be a "good influence".

Wanting the best for one's children is such an atavistic impulse that parents are willing to spend the money in pursuit of subjective outcomes.

There's not much logic to it. Interestingly some of the highest-quality government schools in the country, those in Canberra, are also the most spurned. The ACT has the highest proportion of children in non-government schools of any state or territory. And this is not because Canberra is full of conservative, private school-loving parents. It's the most reliably Labor-voting government jurisdiction in Australia.

But what Canberra does have is high average incomes compared with the rest of Australia. It would seem that income, more than any other factor including political belief, is the determinant of whether parents are likely to send their children to a non-government school. In other words if you can afford the fees there's a good chance you will go private.

So what are the determinants of how well your child will do at school if it's got nothing to do with whether education is public or private? Low birth weight (under 2.5 kg) is associated with poorer NAPLAN outcomes, the UoQ study found. Also, both parents finishing year 12 is linked to better school results for their children.

Another factor is how many hours a week the mother works. More work hours correlates to poorer school performance. My guess is that this is not necessarily related to the gender of the parent. Because most families rely mainly on the father's income, with the mother's likely to be the one that rises and falls depending on family demands and responsibility, this result probably just means that an engaged parent, readily available to their children, leads to better NAPLAN outcomes.

Is that so surprising? What it does mean, however, is that it's not a sound decision for parents to increase their working hours in order to pay for private school fees. It just means your kids are going to do worse at school.