Education Minister Huw Lewis has insisted success in PISA tests is key to the future of Wales' economy.
In plenary today, Mr Lewis said: "Andreas Schleicher of the OECD is absolutely correct when he said - 'Your education today is your economy tomorrow'.
"The cost of a low skills base is potentially huge to the Welsh economy. I can't emphasise enough how important it is that we equip our young people with skills that translate to the workplace and life.
"We want to be a highly skilled nation delivering on our jobs and growth agenda. Welsh workers should have the skills employer's value and want; skills for long term employment - a better grasp and understanding of literacy, numeracy, problem solving and reasoning. The skills that PISA assesses.
"I want that message to be heard loud and clear. Schools, parents and teachers need to understand the wider ramifications of PISA.
"It's not testing for testing sake, it's a way of us seeing exactly where we are in the world and whether we are giving our young people the skills to support the economy and skills to find work in the future."
PISA tests are put on by the Organisation for Economic Co-Operation and Development (OECD) and look at the key skills of half a million 15-year-old pupils from 68 countries.
They are meant to test whether pupils are being adequately equipped with workplace and life skills, with the questions focusing on real-life scenarios. They are hugely influential, though critics say they form just a small part of a much bigger picture in terms of education.
Figures published in December revealed Wales has fallen further behind the rest of the UK in the three areas of maths, reading and science.
Michael Davidson from the OECD - the organisation behind the PISA survey - says pupils' social background is not a leading factor in educational performance in Wales.
Mr Davidson said: "Unlike in some countries where your social background really makes a difference to your success in education, that's not such an issue in Wales. It's more of a challenge to address the under-performing students."
Shadow Welsh Secretary, Owen Smith, has described the PISA results for Wales as 'disappointing' but says that 'the Welsh Labour Government has already recognised the scale of the challenge we face and has put in place the measures required to turn things around.'
He added that
The response of the Welsh Government to today’s results has been honest, serious and long-sighted, in contrast to the short term, party-political points which Conservative UK Cabinet Ministers have sought to make today. Using the education of Welsh pupils, striving for attainment in some of the most challenged and deprived communities of Britain, as a means to score points off the Labour Party, is a cheap trick which will be seen for what it is by the Welsh people.
There are two problems for the Labour politicians running the Welsh Government. Firstly it is they who made PISA results such an important measure of progress in education and it's they who have been in charge of education here since the Assembly began, even when it was run by coalition governments.
The first is why the First Minister and Education Minister made no attempt to portray the figures as anything other than a disappointment. The second explains why opposition parties joined forces in the Senedd in a rare concerted attack on the First Minister. But watch Westminster closely too.
You'd expect Tory MPs to pin the blame on Labour. But it was Labour's Shadow Education Secretary who said that 'Wales has some difficult questions to answer' and some Welsh Labour MPs are also privately worried. You can be certain that they'll let their Cardiff colleagues know their concerns.
Owen Hathway, Policy Officer for NUT Wales, says today's PISA results are 'disappointing' but 'not unexpected'.
He added: "While they are a snapshot, and an important one, they probably don't accurately reflect the entire system as it is - and certainly not as it's going to be, once the reforms that were previously brought in are bedded in effectively."
First Minister Carwyn Jones has acknowledged that the PISA results for Wales are 'not good enough.' Responding to criticism from opponents during First Minister's Questions, he listed reforms that the Welsh Government had introduced since the last set of PISA figures.
But he agreed the figures were 'disappointing' and accepted the need to improve but said it will 'take some time for these measures to bear fruit.'