Proposals for a national reading test could prove to be a "costly" and "backward" step that would fail to improve standards, according to teaching unions.
The test, designed to ensure fewer pupils fall behind in their reading age, was announced last week as part of a landmark speech by education minister Leighton Andrews.
It was prompted by the 2009 Pisa global rankings, in which Wales's mean score for reading was significantly lower than the average.
The test will be introduced as part of the Assembly government's national literacy plan, which will include a focus on seven to 11-year-olds and catch-up reading programmes.
Mr Andrews said abandoning Sats was not "a signal for anything goes". "I expect all teachers to be teachers of literacy," he said. "Pisa has demonstrated that our classrooms are not delivering for our young people. Too few are able to apply the skills they are learning."
But Nick Griffin, Welsh director of teaching union Voice, said the test could be a "very expensive exercise to produce yet more league tables".
He said: "Wales has a good track record in reducing its pupil testing regime so this could be a backward step and very costly at a time when public expenditure is being cut.
"A significant investment will be required in order to construct and pilot such a national test and to determine its validity and reliability."
He said teachers are the best judges of how well children are reading, and test results would produce information teachers already know.
NASUWT general secretary Chris Keates called the proposal a "knee-jerk and unnecessary overreaction".
"Punitive monitoring regimes contribute nothing to educational standards any more than weighing a pig makes it grow," she said.
But Professor David Egan, of the Cardiff School of Education, said a standardised reading test was needed.
"Schools and local authorities use a range of different reading tests, which makes comparisons between schools difficult," he said.
DCELLS REFORM: Frank on failings
In last week's speech on the future direction of education in Wales, Leighton Andrews said the Department for Education, Lifelong Learning and Skills (DCELLS) has been "culturally and geographically fragmented without a clear focus".
"Historically, civil servants have been strong on policy design, but less good at policy implementation and embedding," he said.
Dr Philip Dixon, director of education union ATL Cymru, said: "The minister's candour about the failings in his own department was a welcome admission that no part of the system is beyond scrutiny."
Writing in today's TES Cymru, Professor Ken Reid, former deputy vice- chancellor of Swansea Metropolitan University, launches a scathing attack on DCELLS: "Some of the people with significant responsibility in the department fall some way short of their counterparts in Scotland and England," he says.
- Original headline: Push for national reading test hogwashed by critics