Primary pupils are spending two hours a week doing practice papers for national English tests, the Government's qualifications watchdog has admitted.
The Qualifications and Curriculum Authority believes children's education is suffering as schools desperate to climb the league tables hothouse 11-year-olds for key stage 2 tests.
The first official survey of revision time found that, in the run-up to the spring assessments in Year 6, 75 per cent of schools now spend a 10th of all teaching time practising for English tests alone.
Most of the 340 schools surveyed began this "focused preparation" for the May tests in the spring term, but some even started in the second half of the autumn term. And, despite repeated warnings to keep practice to a minimum, many schools spend further time drilling children for the maths and science tests.
The QCA said it was unlikely that conventional English lessons were being cut back to make room for practice. Instead, schools were slashing time spent on non-tested subjects such as history and design and technology.
Official figures have already shown that schools spend half of the week on English and maths in key stage 2. Sue Horner, QCA subject officer for English, said practice work was likely to increase this figure.
The survey, which represents one of the first attempts to assess how much time schools spend rehearsing for tests, was published as part of an annual QCA monitoring report on English for the year 2002-3.
The QCA said: "Teachers ... told us they were spending too much time on (test preparation) as a result of feeling the pressure to improve...
results in order for the school to appear to be doing well in the published league tables."
A considerable minority of heads were concerned that breadth and balance of the curriculum were suffering as a result. The QCA appears to agree.
Ms Horner said: "We are concerned that, because of the emphasis on the tested subjects, there is a squeeze on other subjects.
"Pupils will be at a disadvantage if they arrive in secondary school having not spent sufficient time on the full range of subjects in the second part of Year 6."
Ms Horner said the QCA and the national primary strategy had been warning schools for two years against extended practice for the tests but admitted that most had not responded.
She hoped that last year's primary strategy, which emphasised the teaching of creativity and enjoyment, would persuade heads that wider work in reading and writing was the best way to prepare for the tests.
Mary Bousted, general secretary of the Association of Teachers and Lecturers, said: "It's naive of the QCA and the Government to say to schools, 'Do not invest inordinate amounts of time practising for these tests'.
"League tables and funding and status depend on schools' performance. Until that changes, schools will continue to devote this amount of time to preparation."
Meanwhile, a separate QCA report on information and communications technology said schools were choosing qualifications "on the basis of points for league tables as much as on the appropriateness of the qualification for the learner".