Some 20,000 GCSE grades were changed this year as the number of queries from schools rose, official figures show.
A separate report found that teenagers were caught cheating more than 4,000 times in this summer's GCSE and A-level exams.
Secondary schools in England, Wales and Northern Ireland submitted 101,100 GCSE grades for re-marking - a 7% increase on 2009.
Of these inquiries, around one in five grades - 20,000 in total - were altered, according to data published by exams regulator Ofqual.
In 2009, 15,009 grades were changed, and all could have been marked down as well as up.
The statistics also show that 14,700 A-level grades were submitted as a "high priority" to be re-marked, because teenagers were waiting on the results to confirm places at college or university.
This was a 4% increase on last year, when 14,157 A-level grades were submitted.
The rise could be down to intense pressure on university places, and teenagers attempting to ensure they receive the necessary grades.
Of those submitted as high priority following this year's exams, one in seven, 2,100 in total, were changed, compared with 1,449 last year.
Ofqual chief executive Isabel Nisbet said: "While any candidate getting the wrong grade is a concern, Enquiries About Results is a rigorous system that exists to ensure that any issues can be appropriately raised and dealt with thoroughly.
"These figures provide invaluable information regarding the examination season. As regulator it is our role to ensure that all candidates are treated fairly."
A separate Ofqual report found that 4,131 penalties were issued to pupils in England, Wales and Northern Ireland for cheating during the June 2010 exam series, representing 0.03% of all the papers marked.
In more than half of cases (53%) students lost marks, while in nearly a fifth of cases (19%), pupils lost the chance to gain a qualification.
In almost three in 10 cases (28%) candidates were given a warning.
The most common offence was smuggling banned items, such as mobile phones, into the exam hall.
The findings show that candidates were punished 1,956 times for taking unauthorised material into exams. Of these, 1,377 penalties were for smuggling in mobile phones or other electronic communications devices.
A further 860 penalties were for copying, collusion or plagiarism, while 372 were for writing offensive, obscene or inappropriate comments on exam papers or coursework.
Students were thrown out 431 times for disruptive behaviour.
There were also a number of other cases, such as obtaining, receiving, exchanging or attempting to pass information related to an exam and failing to follow instructions.
Ofqual's report also shows that 79 penalties were issued to teachers and other exam staff for cheating, the majority of these were because they had given students help.
Ms Nisbet said: "Any incidence of malpractice is a serious concern and a priority for Ofqual. As regulator it is our role to ensure that fair systems are in place and that these are followed correctly. There are clear and severe penalties in place for any candidate or centre that does not follow these systems."
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