Wales awaits Pisa education rankings outcome
2 December 2013 Last updated at 20:36 GMT
Wales will find out how its education system compares to other countries in the world when the latest Pisa results are published on Tuesday.
The tests look at reading, writing, maths and science abilities of 500,000 15-year-olds from around 70 countries.
In 2010, Wales was 40th for maths, 38th for reading and 30th for science out of 67 countries that took part and was also ranked lowest of the UK countries.
It is expected to have slipped down the table again this year.
Education correspondent Arwyn Jones explains the importance of the results.