Pupils at a County Derry school were given the wrong exam results following a blunder. The mistake was made by the English-based board charged with marking the papers.

Eighteen out of 22 Lower Sixth form students of English Literature at Dominican College in Portstewart had their AS-Level grades upgraded, some rising from an E to an A after the school queried their poor performance.

The examination body, Edexcel, blamed an administration error for giving out the wrong marks. It apologised for the distress caused to parents and pupils during the month-long time lapse between the first grades being sent out and the correct results being issued at the end of last week.

The mix-up is the latest in a series of mistakes made by boards in both A-Levels and the new AS-Levels. Fern Turner, of the Association of Head Teachers, expressed concern that the system was over stretched.

"When you are talking about mistakes from E and D right up to A then we are talking about a very, very serious issue," she told BBC Radio Ulster. She added: "That isn't just a simple mistake, that is a fundamental error that could have long lasting effects on that young person's future career."