Wales has slipped down in the international education rankings and fallen behind the rest of the UK significantly in reading, maths and science for the third time. The Pisa tests in science, maths, reading were taken by 500,000 15 year olds in 65 countries. Although the scores for Wales are similar to those in 2010, other countries have performed better. In maths Wales is now ranked 43rd and although there was a higher score for reading this time, it is now 41st and for science, joint 36th. Education correspondent Arwyn Jones reports. Wales' Pisa rankings are worst in UK