So it seems parents are willing to pay a premium of almost 20% on house prices in order to get their children places at good comprehensives.

That, at least, was the conclusion reached by researchers from the University of Warwick this week.

They studied house prices in two areas of Coventry and found that homes in a location within the catchment area of two popular schools were worth between 15% and 19% more than similar homes lying just outside these areas.

In cash terms the extra price of an address guaranteeing admission to the popular school was as high as �20,000.

Of course, as that house price premium is likely to be recouped when the home is sold, this is effectively a refundable price of admission.

On this basis, a �20,000 "investment" - likely to increase in value with the house price index - is a better bet than non-refundable private school fees, at between �6,000 to �12,000 a year for seven years.

Playing the system

The Warwick University research may only confirm what most people assumed to be the case - the middle-classes are adept at playing the system, especially when it comes to school places.

And recent government policies on parental choice have encouraged this "admission-by-mortgage" system.

Policies introduced by the Conservatives - and continued by Labour - have ensured that local education authorities cannot create artificial catchment areas designed to broaden the social intake of a school.

Distance from home to school is now the main factor determining admissions in comprehensive schools.

'Estate agent ploys'

Estate agents know just where the dividing line will fall. A few yards one way and you're in, a few yards the other and you're out.

Allowing parents to state a school preference, and permitting popular schools to expand, has created a market in school provision.

Yet it is not a perfect market since the most popular schools cannot expand sufficiently to embrace all who want to go there. If you cannot "buy" the most popular brand it is not a true market.

The only way to ensure a real market would be to have a lot of spare capacity in schools - yet surplus places are financially wasteful.

Informed choices

Alongside the growth of this pseudo-market there has been a proliferation of consumer information - league tables, Ofsted reports, and glossy school brochures.

The consumer - or "parent", if you insist on being old-fashioned - can now make more informed choices.

One result of this has been to increase demand for places at good schools.

But as competition for places grows, the catchment area shrinks and - at the most popular schools - you must live within a few hundred yards to get a place.

As the geographical catchment area narrows so too does the social class make-up of a school.

The school on the up-market, executive-style housing estate now no longer has places left over for children from the council estate further off.

Transporting pupils

Short of the drastic option of transporting pupils from poor to wealthy areas, (and we know about the political problems that caused in America), this sort of competition for places is likely to reinforce existing social divisions.

In educational, rather than social, terms this might not matter so much if it were not the case that social class impacts on educational achievement.

The government of course likes to tell us that social background is no excuse for low achievement in school and points to the success of some schools which have done well "against the odds".

But while social background should never be an excuse for low expectations, leading to self-fulfilling low achievement, that does not make it irrelevant to educational achievement.

Indeed, most research suggests it is a vital factor.

1980 research

For example, a study in 1980 showed that whereas 39% of pupils from middle-class backgrounds achieved 5 good O-levels, only 12% of pupils from working class homes achieved this level.

Educational achievement is not the same as intelligence.

A study in 1990, which looked at a group of sixth formers with equally high IQ scores, found that on average those from middle class homes achieved better A-level results.

So a good school whose intake is skewed to lower socio-economic groups will almost certainly struggle to get results as good as a similar school serving a more advantaged area.

Parents will then consult league tables and seek to enter the school with the higher ranking.

Polarisation

The result: house-price admission comes into play as it has in Coventry and the polarisation continues.

Finding another way of deciding school admissions is highly problematic.

Zoning, banding or bussing have all been tried, but they conflict with parental choice.

One school did try introducing a lottery to decide admissions - placing pupils' names into a hat - but that was found to be illegal.

So, until we can find a new way, it seems ability to pay will be as applicable to parts of the state school system as it is to private schools.