The planned boycott of primary school league tables is set to go ahead, according to headteachers, who claim that a “staggering” number of governors will sabotage the Government’s plans to publish national test results.

The latest figures from the National Association of Head Teachers show that half of the schools answering its survey say their governing bodies are ready to block the publication of key stage 2 test results.

The response is a substantial boost for the union in its campaign to obstruct the controversial league tables which the Government wants to compile from 11-year-olds test scores.

The NAHT claims that the proposed league tables are politically motivated and educationally unsound. It has appealed to governors of the 25,000 primary schools in England and Wales to act against the Government by refusing to pass on schools’ own assessments of their pupils (conducted by the class teacher).

These were to have been published alongside the results from externally marked tests. Schools must give the results of their teacher assessments to the official marking agencies by July 31.

According to John Kenward, chair of the NAHT’s Curriculum and Assessment Committee, 900 of the 2,000 schools which have responded so far say that their governing bodies will join the protest. A further 900 will comply, many under duress. Two hundred schools are undecided.

“It is a staggering response,” said Mr Kenward. “It is a substantial vote of no confidence in the whole league tables exercise.

“This means that teacher assessments cannot be included in the official figures and also that the externally marked test results will not be checked by the school.”

The NAHT’s campaign has concentrated on the Government’s U-turn in February, when Education and Employment Secretary Gillian Shephard announced that there would be league tables for primary schools, only 10 daysafter she had said that there would be no league tables because the tests were not “fully bedded down”.

The heads’ union has limited room for manoeuvre - there is little it can do to prevent the Government getting results from the externally marked tests. It has also attracted criticism from governors’ organisations. They argue that it is hypocritical to ask governors to break the law while urging teachers to keep to their contracts and administer the tests.

The NAHT replies that governors are not so legally vulnerable as contractually bound headteachers and can therefore stand up to the Government.

* The solution given for the mathematical problem in the report on page 2 of last week’s TES, “Venn circles that made heads spin” was incorrect. The key stage 1 examiners required: an even number of 100 or over; an even number of less than 100; and an odd number of less than 100.