Doug McAvoy, general secretary of the National Union of Teachers, is to recommend the action to the union's executive following a members' survey which suggests widespread opposition to the curriculum tests for seven, 11 and 14-year-olds.
Before a ballot can take place the NUT's leaders have legal issues to consider. However, John Bangs, the union's head of education, said: "I think we will go for the ballot. But there is a window of opportunity for the Government. We are asking it to conduct a survey of all teachers and give us the fundamental reviews of testing we have had in Scotland and Wales.
"The English system is totally outdated and it is the Government that is isolated. The evidence is stacked against them."
The survey, by Warwick university, showed 75.8 per cent of all members replying supported a ballot to boycott tests for seven-year-olds, while 80.7 per cent of teachers of that age group agreed.
For 11-year-olds the figures were 66.1 and 70 per cent respectively. For key stage 3 support for a ballot among those responding was 56.4 per cent, it rose to 80.8 per cent among KS3 English teachers and 56.6 and 60.4 per cent respectively for maths and science teachers.
The NUT's national executive will make its decision when it meets next month. It will have to be satisfied that a boycott will meet the legal definition of a trade dispute, otherwise the union could face claims for millions of pounds of damages from employers or aggrieved parents.
But the head of steam that has built up for a boycott among activists since the Easter conference, combined with the pressures of the general secretary election campaign, will make it difficult for executive members to say no.
More than 14 per cent of surveyed members said they would change their view on a ballot if other unions joined in, but they are unlikely to do so. Both the Association of Teachers and Lecturers and the National Association of Schoolmasters Union of Women Teachers believe a boycott would be unlawful and the NASUWT also argues that piloted changes to KS1 should be given a chance.
The NUT has nearly 260,000 members of whom 31,000 responded to the survey.
Mr Bangs said this was the standard response to a detailed questionnaire.
It found only 6.2 per cent of members replying thought the tests were a reliable way of evaluating pupils, 4.9 per cent thought they raised standards and 5.5 per cent thought they helped to diagnose learning needs.
One respondent, a head of English for 32 years, called the tests "irrelevant, time-consuming and de-motivating". A newly-qualified teacher admitted to teaching to the test.
Nearly 90 per cent thought the tests diminished access to a broad curriculum, 84 per cent that pupils found them stressful and the same proportion saw teacher assessment as a credible alternative.
* Of 242 teachers surveyed by the Qualifications and Curriculum Authority, 62 per cent said that KS2 tests had not been improved by changes. At KS3, three-quarters of 130 respondents said changes to the Shakespeare paper had not been an improvement.
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