Doug McAvoy, general secretary of the National Union of Teachers, said an all-out assault by an alliance of the three big teachers' unions would leave John Patten, the Secretary of State for Education, with no choice but to back down.
NUT leaders last night backed a boycott of all this year's tests for 14- and 7-year-olds. Delegates at the union's annual conference which opens today in Brighton look certain to follow the other two main teaching unions in agreeing to ballot members on a boycott.
Mr McAvoy threatened continued action in 1994 if the Government persisted in testing that was 'educationally unsound' and imposed excessive workload on teachers. Until yesterday the NUT executive had been careful to limit proposed action to a boycott of the Key Stage 3 English tests for 14-year-olds.
Mr McAvoy said that Mr Patten's decision to order a review of the curriculum and assessment arrangements meant there was no point in holding tests this year because the results could not be compared.
The promised review under Sir Ron Dearing, incoming chairman of the School Curriculum and Assessment Authority, has done little to mollify teachers irritated by frequent changes and increased work. The National Association of Schoolmasters Union of Women Teachers has already begun a boycott of preparation work for the tests and head teachers' organisations have made it clear they will do nothing to circumvent industrial action by their staffs.
The moderate Association of Teachers and Lecturers union spurned a plea by Mr Patten to its conference this week.
Delegates voted to ballot members on action to 'limit workload'. The motion did not specify the Standard Assessment Tasks, but Peter Smith, the association's general secretary, said that action to limit workload would 'almost inescapably' mean a boycott of the tests.
Ministers' only hope of avoiding disruption of tests for 14-year-olds in English, maths, science and technology depend on Wandsworth council persuading the Court of Appeal that a teachers' boycott is illegal.
But Mr McAvoy said that although a Court of Appeal reversal might alter the action that union members took, it would not necessarily prevent it. 'We will find a way of bringing home to the Secretary of State via parents that we still want the tests abandoned,' Mr McAvoy said.
He predicted pressure on Mr Patten from Conservative MPs to back down over testing.