Teachers will need time to adapt to the new assessment system which is replacing national tests for 11 and 14-year-olds, opposition politicians warned this week.
But claims by the National Association of Schoolmasters Union of Women Teachers Cymru that the abandonment of Sats will lead to an increase in teacher workload were dismissed by education and lifelong learning minister Jane Davidson.
The move has been widely welcomed by unions and educationists on both sides of the border. Wales abandoned tests for seven-year-olds in 2000, and the latest developments cement a clear difference with England over the value of testing at seven, 11 and 14.
In line with the recommendations of Professor Richard Daugherty's review group, 11-year-olds will not have to take tests in 2005, although new "learning skills" tests are to be developed for 10-year-olds. Next summer's 14-year-olds will be the last to take compulsory key stage 3 tests.
Instead, pupil progress will be monitored via a beefed-up system of moderated teacher assessment, accredited by ACCAC, the curriculum, qualifications and assessment authority.
However, Janet Ryder, shadow education spokeswoman (Plaid Cymru), told the Welsh Assembly government this week that the two in-service training days set aside were not enough for teachers to get to grips with the reformed system. She told Ms Davidson: "We should be looking at increasing the time available for staff to develop the skills to get consistency in the assessments."
Tory Assembly member David Davies said it was vital that teacher assessments were consistent throughout Wales.
"We should be absolutely certain that we have a system where we can see if a school is doing well or badly," he said. But he added: "I have not found a single teacher in Wales who has a good word to say about Sats."
Gethin Lewis, general secretary of the National Union of Teachers Cymru, said: "This is a very happy day for primary children and teachers in Wales.
These tests are flawed, they add stress to children, they overload teachers and they don't help with the transition from primary to secondary.
"Education in Wales is now leading England. I'm sure our colleagues will be looking jealously across the border."
Anna Brychan, director of the National Association of Head Teachers Cymru, added: "It is time to trust the professionalism of teachers and school leaders and their expertise in assessing and developing their pupils' learning.
"In our experience, Sats have offered little of value in terms of adding to a school's body of knowledge about individual pupil achievement. They have also led to a destructive build-up of pressure on pupils and teachers."
But Geraint Davies, secretary of NASUWT Cymru, said its members were concerned that new moderation arrangements for teacher assessments will add to their workload.
"Many are now saying the devil you know rather than the devil you don't.
Our secondary members say to some extent they do teach to the test, but it is part of the national curriculum and the tests are externally marked.
"That burden does not fall on us - whereas increased teacher assessment would."
Ms Davidson told the Assembly that Sats had put teachers under pressure to teach to the tests and led to a narrowing of the curriculum, particularly in the last year of primary school. Announcing the extra in-service training days, one each in 2005-6 and 2006-7, she said: "The move to this system must be gradual and managed. ACCAC will be leading on design and delivery of the new tests and moderation arrangements."
She said that retaining KS3 Sats in 2005 would "provide a necessary measure of quality assurance before we start to build up the new teacher assessment moderation arrangements and the removal of the tests".
And she was confident that the new education package would deliver an "effective, secure and consistent assessment system.