The Qualifications and Curriculum Authority (QCA) said evidence from trial runs of this year's National Curriculum tests indicated that the number skills of 11-year-olds were better than last year.

Although the government's National Numeracy Strategy does not officially begin until September, some schools are already using the new methods - including a daily "numeracy hour".

The QCA's Chief Executive, Nick Tate, said it was too early to predict how children were going to perform in this year's tests, which begin next month.

"But the evidence we are picking up from pre-tests shows that mental arithmetic is becoming a more routine feature of the daily lives of children at school, and we hope that will have some effect on results," he added.

Ministers have focused on the performance of 11-year-olds in maths, aiming to increase the proportion reaching the accepted level for their age to 75% by 2002.

But last year, just 59% of 11-year-olds reached this level - a fall of three percentage points on 1997.

New test

The Education Secretary, David Blunkett, said at the time that a rigorous new mental arithmetic test was to blame for the decline.

However, QCA officials now say that detailed analysis shows that mental arithmetic questions could account for only one third of the slump.

The rest could not be put down to any one cause, apart from the varying ability of different year groups of children.

A spokesman for the Department for Education said Mr Blunkett stood by his comments.

"Discussions which civil servants have had with schools show that if the direct impact was only a one percentage point drop, there was also an indirect effect," she said.

Preparing for the new tests had taken "a lot of time" in schools, she added, giving teachers less time for other maths lessons.