Primary schools have missed the Government's target of 85 per cent of 11-year-olds achieving level 4 in national English and maths tests, annual results were expected to reveal this week.
Results are predicted to have nudged up from last year's figures of 79 per cent in English, with writing expected to have improved by more than reading. Maths and science results are also thought to be up.
The figures, though welcomed by schools, are embarrassing for ministers, as the 85 per cent target had already been put back from 2004 to this year after results reached a plateau.
English results are likely to show at least 80 per cent of pupils achieving the expected level 4, meaning that ministers have finally reached targets that were originally set for 2002.
Failure to achieve these goals contributed to the resignation of Estelle Morris as education secretary that year.
Teachers' leaders have described this year's targets as unrealistic and said this summer's results should be celebrated.
John Bangs, head of education at the National Union of Teachers, said: "We have always said that these arbitrary targets distracted from genuine and real success. Schools were always going to find it difficult to get the last 15 to 20 per cent changed to level 4s."
The TES can reveal that the Government could be facing an investigation from the Statistics Commission after it put back the release of the figures by two days.
The key stage 2 statistics were published yesterday on the same day as improving GCSE results were released, after The TES went to press.
For the past three years, the figures have been released on the Tuesday before GCSE results, meaning the two sets of figures have not had to compete for media attention.
David Willetts, shadow education secretary, said: "Many people may suspect that this is a device to bury bad news. If so, it would not be the first time the Government has sought to bury bad news in this way."
Richard Alldritt, chief executive of the Statistics Commission, said: "The commission regards it as important that statistics are released to the general public as soon as they are ready to be released.
"Any suggestion that that practice is not being observed will be investigated by us."
A spokesman for the Department for Education and Skills said Malcolm Britton, its head of statistics, decided when the results would be released. They were published as soon as they were ready, he said.
The timing of publication was announced in July, before the results were checked, The TES has learned.
From 2008, national KS2 and 3 results could dip by up to 3 per cent after the Government finally bowed to pressure to change the way papers are marked.
At present, scripts with marks falling just below the boundary of a level after first marking are re-marked to check the original score was right but those just above are not. In two years' time, those falling just above a level will also be re-marked.
A spokesman for the Qualifications and Curriculum Authority, which has been lobbying ministers for more than a year to make the change, said it would make marking more accurate.