A dramatic gap has opened up between reading ages in different schools as intakes have polarised between predominantly middle-class and deprived children, according to new research by an early-learning specialist. In 1980 the average difference in reading age between the two types of school was six months. Last year it ranged between 15 months for seven-year-olds to a full two years for pupils transferring to secondary schools.

And despite a series of performance-raising initiatives, overall reading standards among primary pupils have failed to improve throughout the past 17 years.

The findings are backed by a separate study by the Child Poverty Action Group which shows that pupils achieving top grades at GCSE in the richest areas are forging ahead of those in less prosperous areas. They are also more likely to stay on in full-time education.

The evidence is likely to intensify debate about the effects of further selection on a school system increasingly driven by league tables. It comes in a week when the Education and Employment Secretary, Gillian Shephard, confirmed there was nothing to stop primaries choosing their own pupils.

The author of the reading study, Dr Elizabeth Hunter-Grundin, an educational consultant and author of an award-winning literacy test widely used in schools, warned of the danger of further polarisation.

“If a school has to choose between a bright middle-class child, already well-educated and with intelligent parents as opposed to taking in a little child who has not been given help or support, it is obvious which one the school is going to take. I think that is a frightening situation.

“League tables make parents feel like failures as well as the children. If the same policies carry through - selection and all the rest of it - there will be even bigger divisions between the haves and the have-nots,” she said.

The disparities in reading progress came to light when Dr Hunter-Grundin decided it was time to check the continuing accuracy of her literacy tests, which have been used to monitor the reading progress of at least half a million children since 1979. So many educational changes had been made during that time that it was felt the tests might need to be rewritten.

Despite the introduction of the national curriculum and testing, no overall change was discovered. “That surprised us. In fact, the results were quite astonishing. You would expect standards to have risen in that time,” said Dr Hunter-Grundin.

What she did discover was an increasing performance gap between the more middle-class schools and those where there were high levels of deprivation among pupils. She believes the only possible explanation for this is the marked increase in the segregation of different socio-economic groups, with parental choice and selection of pupils concentrating middle-class children in a smaller number of schools. There was no evidence of a fall in standards in schools at the lower end of the socio-economic spectrum. But overall, standards remain the same because there are fewer children in schools between the two extremes, she said.

Dr Hunter-Grundin, who has worked as an educational consultant in the United States, including the Bronx, for the past 15 years, believes the research disproves the theory that selective education raises standards.

The literacy findings are strongly supported by statistics released by the Child Poverty Action Group. The proportion of pupils in poorer areas gaining five or more A-C grades rose from 20 to 32 per cent between 1988 and 1996. However, there was an even bigger jump in the numbers reaching that benchmark - from 30 to 48 per cent - in the most prosperous local education authority areas.

CPAG’s report, Britain Divided, also reveals that although the number of 17-year-olds in full-time education has risen everywhere since 1988, the increase is most marked in areas with the most non-manual families - a rise of 27 per cent, compared with 18 percentage points in the most working-class areas.

It also finds that market forces in education have disadvantaged the poorest children. “Individual school results suggest that in some areas there are schools with increasing proportions of socially disadvantaged pupils, some of whom have been excluded by other schools. Some schools may find themselves trapped in a vicious circle, with the local authority having limited capacity to help.”

It says vast amounts of cash have been poured into league tables but rather less into school improvement programmes, and believes parental choice may be counter-productive.

The proportion of children receiving free school meals rose by 50 per cent between 1991 and 1995, from 821,400 children in England (about 11 per cent of pupils) to 1,235, 746 (17 per cent of pupils, of whom 19 per cent are primary children, 13 per cent secondary, and 36 per cent special school pupils).

The research confirms that education funding does not always match social need. The authors of the education chapter - George Smith, Teresa Smith and Gemma Wright, of Oxford University - conclude that some disparities in LEA funding appear unjustifiable.

“In 1996-97 Harrow has a higher additional educational needs score - implying greater needs - than Barnsley, and Westminster more than Birmingham or Liverpool.”

David Blunkett, Labour’s education spokesman, commented: “The Conservatives have never been interested in the education of all children. Their policies talk about grammar schools for the few and secondary moderns for the many. They have refused to set literacy targets for all children in the way that other successful economies have.” He said only Labour, with its Education Action Zones, intended to target disadvantaged areas.