When the Labour MP Alice Mahon rose to defend her beleaguered local secondary school during the last days of Conservative government, there were murmurs of assent from her Commons colleagues.
Schools like the Ridings in Halifax, which had made headlines after a total breakdown in discipline, had fallen foul of market forces, Ms Mahon argued.
"All on the pretext of parental choice - what rubbish!" she said.
"Does the secretary of state seriously believe that parents who sent their children to the Ridings had a choice? Of course they did not. Choice is a sham."
But was she right? For much of the 1990s the belief that increased parental choice had led to greater social polarisation between schools was received wisdom. Few disputed that competition meant choice for the pushy and the well-heeled. Last month, a report from the Office for Standards in Education called for immediate action to close the gap between popular and unpopular schools and said that challenging pupils should be shared out more fairly.
But two major studies published this year found little or no evidence to support the view that polarisation is increasing. They said schools like the Ridings, since rescued from the problems it experienced as it struggled to cope with an intake of the poorest and least able pupils, were the exception rather than the rule.
Although the findings are highly controversial, they are hard to ignore.
Teams of researchers from the universities of Cardiff and Lancaster, working separately from one another, both concluded that parental choice of schools did not lead to increased segregation.
But this does not mean middle-class parents are failing to push their children into the most successful schools, according to the professor who led the Cardiff study. It simply means they were doing so before and have continued to do so since.
Stephen Gorard and his team examined free meals data for all schools in England and Wales for a 12-year period from the implementation of the 1988 Education Reform Act. They found levels of segregation were actually lower at the end of the period than at the beginning.
Cases like that of the Ridings, where a school spiralled into decline, had always been rare and continued to be so, they said.
According to Professor Gorard, the system of "banding", introduced by the old Inner London Education Authority and still used in a few boroughs, gives schools a broader social mix. Under this system, each school is allocated a proportion of lower, middle and higher-ability pupils. But the catchment areas used in most local authorities before 1988 were no more socially equitable than what followed.
"It was selection by mortgage," Professor Gorard says. "The idea that somehow the middle class have become pushy post-1988 is wrong. They always were.
"The point at which we started was to ask what effect choice would have on a heavily segregated system. We found it had clearly failed to cause more segregation."
His team's findings are supported by similar research from Lancaster university. There, professors Steve Bradley and Jim Taylor did a similar analysis. Their results were slightly different - they did find a slight increase in polarisation since 1992. But they concluded the effect was small and was more than counterbalanced by the beneficial effect of competition on standards.
"We find that the introduction of market forces into secondary education since the early 1990s has had a beneficial effect in raising educational performance. Moreover, there is little evidence that this improvement in performance has been achieved at the cost of any significant increase in the polarisation of pupils between schools," they concluded.
The findings remain highly controversial within the academic community.
Alex Gibson of Exeter university called Professor Gorard's measure of social segregation unreliable. His research suggested that the results of the top 10 per cent of schools were improving at nearly three times the rate of the bottom 10 per cent.
Professor Anne West, director of the Centre for Educational Research at the London School of Economics, argues that the free school meals data used by the two studies may have varied because of changing economic cycles.
"As far as I am concerned we don't know the truth at this stage because it is difficult to interpret the results," she says. "I think Stephen Gorard and I would agree that segregation has increased in some local authorities, particularly those where there are a high proportion of schools responsible for their own admissions."
Research published recently by Professor West does indeed concur with Professor Gorard's findings on this last point, and also goes some way to explaining the fact that although he found segregation dropped under the Tories, it rose slightly under Labour.
Her research into admissions policies, found the expansion of the specialist schools programme had led to increased selection, a finding which Professor Gorard supports. And both agree that schools which control their own admissions - voluntary-aided and, until this year, foundation schools - are likely to have a higher proportion of middle-class pupils.
Professors West and Gorard believe this increasing diversity has had a negative effect on schools whose neighbours have introduced partial selection by aptitude, or which insist on interviews with parents or children.
"Where you have schools that are able to be more selective than others, where do the pupils go who are in care, have special needs or are low achievers, or who have parents that are not supportive? That has consequences for other schools," Professor West says.
On this point Alice Mahon was right, for she pointed to the existence of local grammar schools as a major contributor to the problems of the Ridings. But while a change in admissions policies might help to smooth out some such problems, it would take a far more radical social reform to solve the most critical factor controlling schools' intakes.
The Cardiff research revealed that the biggest single factor controlling the social mix of schools was not admissions policies but housing. And again it came up with something startling.
Social segregation - measured by taking the level of free meals in a school compared with its neighbours - was greater among rural schools than urban ones.
This was partly because city children were more likely to have a choice of schools than rural ones, but also because rich and poor were more likely to live cheek-by-jowl in cities than they were in the country.
But if the area a child is born in is so important in deciding where he or she will go to school, surely that alone must have led to increased social polarisation? Some experts say housing has become increasingly segregated in recent years, with subsidised housing now largely the last resort of the very poor.
Twenty years ago, nine out of 10 families moving into social housing were headed by someone in full-time work. Now the figure is just one in four. So surely schools in areas with large concentrations of social housing must have increasingly impoverished intakes?
Not so, according to Professor Steve Wilcox of York university's centre for housing policy. He says the received wisdom is as misguided on social segregation in housing as it now appears it may be in education.
There has been increasing polarisation between different types of housing, he says, but that does not mean the country has been divided up between owner-occupied housing for the well-heeled and sink estates for the poor.
Because the Thatcherite "right to buy" legislation put many council properties into private hands, owner-occupiers now often live next door to families in social housing - and their children attend the same schools.
Although there are still sink estates where few residents wanted to exercise their right to buy, the housing map of Britain is not as bleak as many experts presume, Professor Wilcox argues. And, likewise, neither is the educational map as riven by the after-effects of Thatcherism as it seemed previously to be.
Schools, markets and choice policies by Stephen Gorard, John Fitz and Chris Taylor, published by Routledge Farmer price pound;70. The Economics of Secondary Schooling by Steve Bradley and Jim Taylor published by the School of Management, Lancaster universitySecondary School Admissions in England: exploring the extent of overt and covert selection by Anne West, H Hind published by the Rise Trust