Thousands of primary schools are set to rebel against a decision to boycott key stage 2 Sats, as even heads who are against the exams say they will administer them anyway.
The opposition to the boycott emerged as the National Association of Head Teachers and NUT decided to back industrial action to disrupt the tests being taken next month. The unions, which have spearheaded an anti-Sats campaign for more than a year, claim they have a mandate following a ballot of members.
Mick Brookes, general secretary of the NAHT, said: "The Government missed the opportunity to reform the assessment for pupils in key stage 2 when it abolished the same tests in key stage 3 in 2008. We cannot continue to have our colleagues and their school communities in the primary sector disparaged on the basis of a flawed testing regime."
But heads spoken to by The TES said the decision on industrial action has come too late and drags children who have prepared hard into a political battle.
There are claims from governors that the boycott could put greater strain on schools than the stress of going ahead with the tests.
And about 329 primaries who are in special measures, or have a notice to improve, will also be wary of taking part, since Ofsted is not yet offering any clear guidance on how opting out of the tests will affect inspection reports.
This week's decision to push ahead with the boycott follows the results of a ballot of almost 24,700 heads, deputies and assistant heads in the NUT and NAHT.
Almost two-thirds of respondents voted in favour of action. Turnout was almost 34 per cent among NUT members and just under 50 per cent for the NAHT. However, only 29 per cent of the total eligible to vote actually said yes - 7,213 out of 24,699 heads, deputies and assistant heads.
Mr Brookes said in-house research had indicated that the ballot result could translate to 4,000 to 5,000 out of 16,000 schools taking part, since waverers may now be inspired to join in. That would leave at least 11,000 schools refusing to take part in the action, but Mr Brookes said those participating would be enough to disrupt the compilation of league tables.
A number of headteachers spoke out against the boycott immediately after the union announcement.
Jeremy Doyle, head of Redhills Community Primary School in Exeter, said that while he was against the testing regime, both he and his staff had unanimously agreed to administer the tests.
"The whole business of testing children in the way we do is deeply flawed," he said. He added that boycotting the Sats for political reasons "smacked of double standards". "Children are being used as pawns in a wider political debate."
Heads who support Sats are more predictably also set to deny the boycott. Andrew Carter, head of South Farnham School in Surrey, which has come top of the KS2 league table for the past two years, said: "I don't think it's good for children to see senior members of staff losing an argument and saying: 'We are not going to do it, then'; it seems like a poor moral lead."
He thought most teachers were "a pretty obedient lot" and loud union voices did not represent the view of the wider profession.
Mr Brookes said the boycott was not "old-style union politics" and merely allowed heads who wanted to take action to do so. Schools who decided to opt out would not be coerced into it, he said.
Clare Collins, chair of the National Governors' Association, said: "Everyone was holding their breath to see what the ballot result was going to be but the process has been so extended and confusing that everyone's got their heads firmly buried in the sand, hoping it will go away. Relationships are being strained on all levels, from the governors to the management team to those administering the tests, and that is before you start to consider the parents."
Schools Secretary Ed Balls said: "It is disappointing that the NAHT and NUT are pressing on with their dispute when the clear majority of heads and deputy heads do not back this action - over two-thirds of their own members did not vote to support disrupting tests."
ACTION AND REACTION
Schools who say they are hoping to boycott the Sats are set to rebel in a number of ways. Some, who still want their pupils to sit an exam, will be handing out copies of last year's test papers. Others will make pupils sit this year's papers, but will not submit them for marking.
Mick Brookes has said some schools may wish to hold an "assessment week", focusing on teacher assessment of pupils.
But some headteachers may junk testing completely. The unions have suggested they may wish to hold an arts and creativity week "to celebrate" this.
The NAHT and NUT want the Government to scrap externally assessed exams for children at KS2, because they put "intolerable pressure" on school leaders and are used for the compilation of league tables.
The unions want the current regime replaced with a national sampling system for maths and English, which has already been done for KS2 science and KS3 core subjects.
They say schools should be allowed to focus on potentially more accurate systems of teacher assessment, and time would be freed up to widen the curriculum.