UK exam board Edexcel has upped the ante in its high-tech bid to thwart teenage cheats.

This year's GCSE and A-level exam season is already underway, and the board is looking to extend last year's use of electronically tagged exam papers.

The names of individual schools will be invisibly written and embedded within single letters of exam papers using so-called 'microtext'.

The watermarking technique helps to limit cheating as the microtext cannot be photocopied. In the event of a breach the paper can be traced back to the offending school.

Edexcel has also announced plans to fit bags carrying exam papers with radio tags to ensure that the tests have not been tampered with, and is looking at recording oral exams using the MP3 format.

The board will continue to use last year's anti-plagiarism software to scan for potentially suspiciously answers.

Edexcel managing director Jerry Jarvis claimed that the chances of cheats getting away with it have fallen dramatically, and that 80 per cent are being caught.