DRAMATIC increases in school standards used by the Government to trumpet its education policies are largely an illusion, according to an expert.

Evidence from a series of long-term studies suggests the real rise is far lower than ministers have claimed.

According to Government figures, the number of 11-year-olds reaching level four - the level used to set targets - in English, rose from 48 per cent in 1995 to 75 per cent in 2000. The improvement in maths was equally startling: from 44 per cent in 1995 to 72 per cent five years later.

But Professor Peter Tymms claims the real increase was from 48 per cent to an estimated 58 per cent reaching level four in English, and from 44 per cent to an estimated 64 per cent in maths.

The apparent rise in achievements for pupils leaving primary school was one of the Government's chief success stories in its first term.

Prof Tymms, director of the Curriculum, Evaluation and Management Centre in Durham University's Education Department and one of the country's leading experts on school testing, brought together the results from a range of studies and compared them with the results of the Key Stage Two tests taken by all 11-year-olds.

He said the data showed that standards had improved, but not nearly as rapidly as the Government claimed.

He said: "It is really a case of the Government saying we have seen a massive rise in standards, but actually a lot of it is illusion, especially in English. In maths, standards have gone up, but not by as much as the Government says."

He said the Qualifications and Curriculum Authority (QCA), which runs the tests, had failed to establish a proper baseline against which any change in standards could be measured.

His conclusions are supported by a study for the QCA, but kept secret for nearly two years, which found that the increase in achievements in English was largely a result of a fall in the standard of the reading test.

Prof Tymms decided to examine the tests after teachers reported they were not seeing the improvement in successive new intakes promised by the official figures.

Tim Andrew, president of the Secondary Headteachers' Association, said Prof Tymms' findings did not contradict the experience of many secondary schools.

He said: "I'm not surprised with these sorts of conclusions. I would not want to go so far as to say there have been no improvements, but to say the improvement is not as great as it seems sounds like common sense to me."

He said that under the existing test regime, teachers become skilled at teaching pupils to do well in tests, meaning test scores could outstrip actual achievements.

But the Department for Education and Skills rejected Prof Tymms' findings.

A spokeswoman said: "Half of all 11-year-olds in 1997 went to secondary school unable to read, write and count well. Now it's a quarter. Independent evaluations of the literacy and numeracy strategies confirm they have transformed the standards of teaching and learning in English and maths since 1998."

A QCA spokeswoman denied its testing procedures were at fault and said the rise in standards in the official figures was an accurate reflection on the improvements made in the past nine years.

She said an anchor test, which had remained the same since 1995, had been used to ensure accurate comparisons were made, and preliminary tests were carried out to ensure standards were maintained year-to-year.