By Gary Eason
BBC News website education editor
The trend in results over recent years
There has been a slight fall in the proportion of 11-year-olds in England reaching the standard expected of them in English national curriculum tests.
In 2009 80% did so, down from 81% last year. This is the first time since 1995 that the results have fallen.
Attainment in maths and science was 79% and 88%, the same as last year.
Science tests are being scrapped next year. Two education unions plan to boycott the 2010 Sats, arguing they narrow the curriculum for children.
Last year the government missed its target for 85% of pupils to make the grade in English and 85% in maths and now it has slipped further away.
KEY STAGE 2 RESULTS
A new target is that 78% will do so in both subjects combined by 2011. This year 72% did - one less than last year.
The test results rose markedly after Labour came to power and introduced literacy and numeracy strategies in England's primary schools.
The English attainment stalled on 75% for four years in a row before recommencing its upward trend.
This year's results are provisional and might change slightly once all the appeals made by schools have been dealt with.
Some would also question the validity of last year's score, given the chaos that afflicted the whole marking process prior to the departure of the test contractor, ETS Europe.
At the higher Level 5, attainment this year was 29% in English (down one percentage point) and down one point in science at 43%.
But the maths results jumped four percentage points, to 35%.
This Level 5 is the attainment more normally expected of 14-year-olds in secondary school.
Sats for 14-year-olds were scrapped altogether last autumn following the widespread delays in marking.
This is the last year that the science test will be taken by 11-year-olds.
Instead teachers will assess their children's progress, the pattern already established in Wales.
As a check on national standards, a random sample of 10,000 pupils will sit tests each year - as is done in Scotland.
Schools Minister Diana Johnson said the fall in the English result was "disappointing".
Primary schools had made very substantial progress in raising standards over the past 12 years, after years of just coasting along - but it was getting tougher to get the final 20% to the expected level.
"This year's results demonstrate loud and clear that we are going to have to ask some hard questions and re-double our efforts if we are to make further progress in national curriculum tests next year and in future years."
There would be early intervention and one-to-one tuition for pupils who were falling behind in English and maths from this September, while head teachers would have more discretion to tailor lessons to pupils' needs.
The minister said she hoped the one-to-one tuition would particularly help boys who were struggling in English.
Michael Gove, Shadow Secretary for Children, Schools and Families, said: "We have seen a historic drop in English results, the brightest students are not being stretched, and the weakest are being failed the most. It is deeply worrying that English results are in decline."
Liberal Democrat schools spokesman David Laws said progress in primary schools had stalled and in some cases had slipped backwards, and the gap between girls and boys in literacy was very worrying.
"One in four boys now starts secondary school without being able to read or write at the expected level."
More girls than boys reached at least the expected level (Level 4) in both aspects of English
A ballot on a boycott of next year's Sats is planned by two education unions.
The National Association of Head Teachers (NAHT) and the National Union of Teachers (NUT) oppose Sats because they say teachers are obliged to "teach to the test".
In a statement the NAHT said: "We believe that the system is simply being maintained through political obduracy and that there are better ways to gain a broad picture of primary education in England.
"We encourage parents to ignore this meaningless nonsense and to work with their schools to ensure that they are not unfairly judged by some inspectors who treat this information as being accurate and therefore prejudge school performance on the basis of an erroneous and narrow set of indicators."
The government has warned heads they have a statutory duty to administer the tests, and a boycott would be illegal.
Chris Keates, general secretary of the Nasuwt teachers' union, criticised "serial detractors" who cast doubt on the tests, rather than acknowledging the hard work of pupils and teachers.
"As sure as night follows day when there is an opportunity to celebrate the achievements of young people and the hard work and commitment of teachers the obsessive opponents of the tests step forward to undermine and cast doubt on the whole process."