UK secondary school students have slipped down an international league table of reading and maths standards.
Pupils in the UK have fallen from an international top 10
Based on test results in 2006, the UK has lost the top 10 positions it held for both subjects seven years ago.
The most successful countries in reading are South Korea and Finland and teenagers in Taiwan and Finland are the highest achievers in maths.
The international study is produced by the Organisation for Economic Co-operation and Development.
These Programme for International Student Assessment (Pisa) performance tables are based on tests taken by 15-year-olds which aim to assess their ability to apply their knowledge in "real world" situations.
They are undertaken every three years - but the UK did not participate in the last round of tests, taken in 2003.
Comparisons instead are made with the UK's ranking positions based on tests taken in 2000.
Last week, figures from the Pisa study showed that the UK had tumbled down the league table for school science.
And the latest report shows that the UK's performance has also declined in both reading and maths against international competitors - going from above-average to average.
It is the only country which was in the top-performing group in 2000 to have slipped down into the lower group.
In 2000, the UK was placed eighth in maths and seventh in reading - the UK in the latest table is in 24th place for maths and 17th for literacy.
The countries which were ahead of the UK in reading in 2000 - Finland, Canada, New Zealand, Australia, Ireland, Korea - remain in the top 10 for this year.
But the UK has now been overtaken by countries including Poland, Sweden, the Netherlands and Japan.
In maths, the UK has been overtaken by a group of improved performers, including Slovenia, Belgium, the Netherlands, Denmark and Austria.
MATHS TOP 10
The Pisa rankings, based on tests taken by 400,000 students in 57 countries, is an attempt to measure the attainment of pupils in different education systems. The tables being published now are based on tests taken by pupils in 2006.
This is the latest in a series of international education tables - in an increasing trend to assess performance against other countries, rather than only using national benchmarks.
This has not brought much positive news for the government.
Last week's leaked Pisa science report showed a decline for the UK.
And the reading performance of 10-year-old children in England has fallen from third to 19th, according to the Progress in International Reading Literacy Study.
An accompanying survey found high levels of concern about safety in school from pupils in England.
The UK government has sought to play down the Pisa findings - saying that the rankings were not comparable with previous years.
SCIENCE TOP 10
Schools Minister Jim Knight said that the science results showed that the UK remained above average.
And for maths and reading, he promised greater efforts to intervene when pupils are struggling.
"We are putting a relentless focus on the progress of every individual through programmes such as Every Child Counts and personalised learning so that we know exactly where progress is made and where children are falling behind," said Mr Knight.
The Shadow Children's Secretary Michael Gove said: "Every year the government boasts about the improvements it has made to education but every external audit tells us we're falling further behind."
The CBI's director-general, Richard Lambert, said the report was "disturbing reading".
"At a time of increasing global competition, the UK cannot afford to be 'average'. We need a renewed sense of urgency in tackling the UK's underperformance in literacy and numeracy," said Mr Lambert.