More than 6,000 candidates received a GCSE upgrade this week after the Northern Examinations and Assessment Board rectified a computer error which had marked 130,000 candidates down.
The results of all modular science and humanities entrants were reviewed after examiners uncovered an error in the computer program which combines marks for coursework, modular tests and final exams.
The mistake came to light when appeals started to flood in.
While the correction raised most of the 6,000 by one grade, around 100 students wrongly graded as unclassified were relieved to receive their correct D grades. They had been entered for the higher exam tiers but, marked as just missing a D grade, they were given a U.
A spokeswoman for NEAB said the board's swift action had hopefully ensured that pupils' A-level choices and employment prospects were not affected.
Margaret Hutchinson of NEAB: "The majority were only brought down by one grade. We made sure all centres were informed of the problem as soon as it was discovered so there was only a week in which they were misgraded without knowing it."