The Assembly Government says it has no plans to take part in the biggest ever global study of pupil achievement.
England was among the top performers in the world for maths and science in the Trends in International Mathematics and Science Study (TIMSS) published this week.
England finished in the top seven countries in all four tests, taken by 425,000 pupils worldwide, its best performance for eight years.
But Welsh officials instead opted to take part in the Programme for International Student Assessment (PISA), which not only tests maths and science, but also literacy for 14-year-olds.
Wales fared badly, lagging behind the other home nations in the 2007 results - the first time they had taken part - ranking alongside Azerbaijan.
"Any future decision to participate in TIMSS or any other international assessment program would need to be considered against our research and policy priorities, and with an eye to tight resources and potential burdens on participating schools," said a government spokesperson.
England's experience with TIMSS, page 18.