Wales has fallen further behind in a worldwide assessment of pupils' maths, reading and science skills.
Welsh pupils are again behind their counterparts in England, Scotland and Northern Ireland in all three areas, and are below the global average in those areas.
Results from the so-called PISA (Programme for International Student Assessment) tests, sat by 15-year-old pupils around the world last year, have been published today by the Organisation for Economic Co-operation and Development.
Wales is now ranked 43rd out of 68 countries for maths, 41st for reading, and 36th for science - all lower positions than when the tests were last held in 2009.
The Welsh Government has previously targeted the top 20 positions of the influential league tables when the next tests are sat in 2015.
Head of the Organisation for Economic Co-operation and Development Angel Gurria has told ITV News "we have to put a big fat price on carbon" to tackle climate change and "we have to start now."
On Chancellor George Osborne's comments that Britain should not be "in front" of the world in tackling climate change, Gurria said: "The UK has been a leader...the problem is the financial crisis is being used as an excuse."
The OECD report on numeracy and literacy in 24 countries said basic skills among young people in England and Ireland were "bound to decline" unless "significant action" is taken.
Although young people in these countries are entering a much more demanding labour market, they are not much better equipped with literacy and numeracy skills than those who are retiring.
The implication for England and Northern Ireland is that the stock of skills available to them is bound to decline over the next decades unless significant action is taken to improve skills proficiency among young people.
Young people in the UK spend nearly two-and-a-half years out of work, one of the highest rates amongst developed countries, according to new OECD research.
The organisation’s Andreas Schleicher said many young people have “given up, more or less” and warned that the "biggest challenge" to the UK was to help those youngsters who do not have decent qualifications.
The figures, for 2011, show that people in the UK aged 15 to 29 expected to spend 2.3 years on average either unemployed or out of the labour force entirely – higher than the Netherlands (1.1 years), Iceland (1.2 years), Norway (1.3 years), Australia (1.7 years) and Germany (1.7 years).