Head teachers have voted to boycott national SATs exams taken by 11-year-old primary school children in England.

Union leaders will decide today what action to take following the vote by senior school staff from the National Union of Teachers and the National Association of Head Teachers.

The Key Stage 2 (KS2) SATs exams in English and maths are scheduled to take place in primary schools from May 10, the week after the general election.

A union official said children would continue to be taught normally during an exam boycott.

Teachers have long objected to the tests which are used to rank schools in England as well as checking the academic progress of pupils.

They say the exams dominate teaching in children's final year at primary school, stifle creativity and impose unneeded stress on teachers, pupils and parents.

They want the tests replaced by teacher assessment of pupils' learning.

The tests, first introduced by the Conservatives in the 1990s, have been a key plank of the Labour government's drive to improve education standards.

The Conservatives, who would keep the KS2 tests if they win the election, say they would experiment with moving them from the last year of primary school to the first year of secondary education.

But the tests are no longer used in Wales, while Scotland does not use them for school league tables.

In England, Key Stage 3 SATs tests for secondary school children aged 14 were dropped in 2009 after delays in the previous year's marking. Science tests for 11-year-olds ended this year and have been replaced by teacher assessment.

The two unions balloted head teachers, deputy heads and assistant heads, who are responsible for running the exams.

The NUT said its members voted 75 per cent in favour of a ballot on a 34 per cent turnout. The NAHT had a higher turnout of 50 per cent, with 61 per cent in favour.