David Hart, general secretary of the National Association of Head Teachers, to which the majority of primary school heads belong, said he had received only three letters of complaint about advice sent to all members not to volunteer to take part in the pilot tests. Teachers are already considering a boycott of English tests for 14-year-olds.
The association says its patience with ministers is exhausted after their refusal to listen to teachers' views and a series of broken promises. It has also told 25,000 heads and deputies that the pencil and paper tests in English, maths and science, lasting four and a half hours, will be unfair to children and cumbersome to administer.
The advice note says: 'It must be demonstrated that the headteachers and deputies of England and Wales are not willing to assist in the introduction of untrialled and unproven assessments.'
Mr Hart accused the Government of backtracking on its promises not to publish the results of pilot tests for seven-year-olds. 'We have no doubt that they will also publish these test results,' he said.
Gerry Wilson, head of the association's education committee, said teachers were angry that the test result was to override four years of complex and laborious teacher assessment of children. 'Children who react badly to test conditions will be penalised.'
John McNicholas, head of Molescroft primary school in Beverley, North Humberside, said that, unlike many previous tests, these had not been standardised so that reliable comparisons could be made between the performance of children in different schools and parts of the country. 'We don't know what average achievement is supposed to be in these tests yet they will be used to label children and schools.'
The Schools Examination and Assessment Council, which is organising the pilot due to take place in the week beginning 17 May, said it hoped to secure the agreement of between 200 and 250 primary schools needed for an effective pilot, just over 2 per cent of the 19,000 state primaries. Schools had been enthusiastic before the boycott was suggested, a spokeswoman said.Reuse content