The biggest teachers' union is to ballot members in England on a boycott of the primary school national curriculum tests next May.
The unanimous decision by the National Union of Teachers executive follows a survey of members which indicated support for a boycott.
TESTING IN ENGLAND
Key Stage 1
End of Year 2 - age 6/7: national tests in English and maths, marked in school, school's results available locally. From 2004, pilot scheme putting greater emphasis on teachers' assessments
Key Stage 2
End of Year 6 - age 10/11: national tests in English, maths and science, marked externally, school's results published nationally
Key Stage 3
End of Year 9 - age 13/14: national tests in English, maths and science (and ICT from 2004), marked externally, school's results published nationally
Ballot papers will go out over the next few weeks to members in all infant, junior and primary schools. The result is expected in December.
Tests in English and maths are taken by seven and 11 year olds. The older children also take science tests.
The survey of members indicated that 82.5% would boycott the tests taken by seven year olds and 71.4% the tests taken by 11 year olds - which form the basis of the primary school league tables.
The boycott will begin in the new term when primary teachers would otherwise start preparing for the tests, the union said.
The general secretary, Doug McAvoy, NUT General Secretary, said: "The NUT has sought a meeting with the government to press for a review of testing in England. It has ignored that request.
"Teachers in England do not understand why they and their pupils should be treated differently from those in Scotland and Wales.
"In Scotland following a review, national tests are to be replaced by teacher assessment. In Wales Key Stage 1 tests have been abandoned and a review of Key Stage 2 and 3 tests is underway."
He said teachers' anger would be fuelled by the government's "stubbornness".
Teachers and parents were tired of the disruption the tests caused to children's education.
"When the boycott goes ahead, no child's education will be disrupted. Instead teachers will be able to use their professional judgement to their pupils' benefit and in support of their primary purpose of educating children," he added.
At Key Stage 3 - the tests for 14 year olds - the survey of members was less in favour of a boycott (64%).
But Mr McAvoy condemned the government's intention to take those results out of the main secondary school performance tables, and publish them separately, as announced this summer.
"In the light of this change, the union will do further work with members in secondary schools prior to a ballot to boycott Key Stage 3 tests," he said.
"In recognition of the review in Wales, the ballot will be confined to members in England. When we know the results of that review, the position of teachers in Wales will be looked at again."
Ministers have repeatedly refused to countenance scrapping the tests in England and reverting to what they call the "dark old days" when people did not know how schools were performing.
The Education Secretary, Charles Clarke, said: "A boycott of tests would be a gross betrayal of children. It would say that we don't care how children are doing or how we can better help them in school.
"We would urge any member of the NUT to vote for children and against industrial action.
"National testing has a very clear moral purpose. It means we have high expectations for every single child.
"It enables schools to tailor their teaching to each child's needs. And we can compare each child's progress with that of other children."
Tests at age seven were being reformed in response to criticisms, to take more account of teachers' assessments - a pilot version runs in some areas next year.
But national tests were here to stay, he said.
The shadow education secretary, Damian Green, said tests were a useful measure of standards for teachers and parents - the real problem was the government's imposition of national targets based on the results.
He hoped NUT members would not back the boycott move - "a disappointing decision and one which could severely disrupt children's learning."
The Liberal Democrat education spokesman, Phil Willis, said: "There is widespread concern amongst parents, teachers, educators and MPs over the current regime of
tests which makes our children the most tested in the world.
"Charles Clarke would be well advised to seek a meeting
with the NUT to discuss their concerns rather than continue his vendetta against their members."
Head teachers urge rethink
David Hart, leader of the National Association of Head Teachers, with a majority of members in primary schools,
said a boycott would have a "massive impact".
He and Secondary Heads Association general secretary, John Dunford, urged the NUT to think again.
Theys aid testing was necessary even though there
were some problems with the way it was done.
The National Confederation of Parent Teacher Associations said a poll of its local members had shown a "significant" number did not want teachers to boycott the tests.
But it agreed that children were "over-tested" and
stressed by the exams.