Bob Howells, head of school effectiveness, says that the virtually unanimous decision shows “intelligence on the part of our headteachers”.

When it was announced that the tests were no longer to be compulsory this year, Jane Davidson, the Welsh education minister, planned to replace them with teacher assessments and a skills test for 10-year-olds*. However, the NASUWT Cymru did not back her plans because, the union argued, the proposals lacked clarity. Last November, Geraint Davies, general secretary of NASUWT Cymru, admitted that Sats were unpopular but said their abolition would leave teachers “faced with the unknown for a good few years”.

And last month the architect of Wales’s assessment reforms, Professor Richard Daugherty, of the University of Wales at Aberystwyth, warned that teachers needed time and training to develop assessment skills.

Mr Howells at Caerphilly points out that after schools withdrew from KS1 testing there was a drop in standards, both locally and nationally. “We were particularly concerned that if we were withdrawing from an assessment that had been used for years to assess children’s attainment and achievement and were putting nothing in its place, that it was a pretty risky strategy. We had discussions with our heads.

“We believe Sats have been particularly useful in analysing some of the under-performance issues,” says Mr Howells. “We have been doing an analysis of our performance, particularly at KS2 and 3, using national curriculum assessments and tests in particular. It has given us insight into what it is that we need to do.

“We think that we have used the information we have from assessment data to understand what the council can do to help youngsters to make greater progress. We have found, by analysing performance data in English, that it conceals underperformance in writing. If youngsters cannot write to the same level that they can read it is going to be very difficult for them to access the curriculum.”

*To be piloted in 2006-7 for implementation in 2007-8