An investigation is underway after pupils piloting new tests in England likely to replace Sats within two years for 11 and 14-year-olds performed badly, The TES has learned.
The Department for Children, Schools and Families has asked the National Assessment Agency (NAA) to look into why the results of the tests, based on a mix of teacher assessment and exams, were not as good as expected.
More than 400 schools took part in trials of the tests. But the Westminster Government has delayed publishing the results until after the NAA probe.
Pupils only sit the tests, which could be introduced in England in two years, when they are thought to be ready for them by their teacher. They sit a 50-minute exam in reading, writing and maths twice a year. Bad results in the new trial tests for England could be blamed on poor teacher assessment of their pupils' abilities, the tests being too hard or simply because the testing system is new.
But experts warned this week that mixing tests under exam conditions with teacher assessment might be a mistake.
In Wales, Sats for the age group have now been abolished and all results now rely purely on teacher assessment. The tests were optional for schools until the end of 2007. Key stage 1 Sats were abolished in 2002.
Although the new tests are trials, the results of the 22,500 pupils taking part count towards league table standings.
David Bell, permanent secretary at the DCSF, told MPs this week: "We have asked the NAA to do some further work. We are not ready to come back with the results of that analysis."