Hundreds of GCSE, AS and A-level results have been re-graded after errors were made in exam marking.
The OCR exam board said it apologised "unreservedly" for the mistakes, which were made by examiners, and insisted that action had been taken.
In total, 98 GCSE, 285 AS-level and 50 A-level results, were revised upwards after being re-marked.
The errors came to light in the autumn and were due to "human and process errors by a minority of examiners", the board said.
Schools and colleges with affected students have been told, OCR said, and they will pass on the results to their pupils.
Chief regulator Glenys Stacey says Ofqal has noticed a pattern in appeals of exam results from schools.
The analysis that we have done has shown that there is tactical appealing at critical grade boundaries - C/D at GCSE and B/A at A-level, that doesn't mean that every appeal at that boundary is tactical, but you can see from the pattern that it would suggest there is tactical appealing.
Secondly, the way the appeal system is designed at the moment, and indeed headteachers agree with us, that where you're within a couple of marks of such a grade boundary it's worth appealing because it is a one-way bet.
Schools are playing the exams system by appealing against results in a bid to improve pupils' grades, the qualifications regulator has said.
Ofqual suggested the current GCSE and A-level appeals process was designed for a "more innocent era" and is being tactically used by teachers under pressure to secure good results.
In a new report it said that evidence suggests an increase in appeals against results, particularly those that are within one or two marks of key grade boundaries - such as C/D at GCSE and A/B at A-level.
It also found that examiners dealing with appeals may be looking for extra marks to award to students as they are conscious that the final result could have a major impact on a youngster's future.
Students sitting their GCSEs will only have results counted from their first exams to stop schools from "gaming" the system to improve their league table rating, the Department of Education announced today according to The Guardian.
Education Secretary Michael Gove claimed some schools were "cheating" the system by allowing students to sit exam papers a year or more before required.
The school is in effect gaming the system by not thinking what is in the best interests of the student but using the student as a means of gathering points so the school itself can look better and that is, in a word, cheating.
Skills Minister Matthew Hancock said the number of children that fail to achieve a C grade in maths and English is "scandalous".
A Government plan to make over-16s who fail maths and English GCSEs continue studying the subjects received a lukewarm response from many readers on the ITV News Facebook page.
Sam Clarkson said the qualifications were not essential for everyone, writing:
I was not academically clever, you could have made me resit until hell froze over and I'd never get a C. I managed my life fine without them.
Emma Carver agreed that some children were simply not cut out for academia, despite its importance, saying:
These days you need maths and English to get any job. I re-took my maths after I left but still didn't get a C grade. You're either good or not, I don't think they should pressure the kids.
However, Vicki Pellatt backed the Government plan - providing there was sufficient funding for it:
Good idea, as long as the young person is supported with their studies maybe with different teaching methods to enable them to understand. This of course means more teacher time and more money...
The head of the headteachers' union has raised "serious concerns" about government plans to force GCSE students who achieve less than grade C in maths and English to resit.
Brian Lightman, general secretary of the Association of School and College Leaders (ASCL) said:
We have been expressing serious concerns to the Government for some time about the implementation of this very significant new policy about which there are many unanswered questions in the absence of a coherent and funded implementation plan.
At a time when post 16 funding is being significantly reduced and feedback from ASCL members continues to show very different states of readiness in different parts of the country it is difficult to see how schools, colleges, employers and local authorities will be able to provide additional classes or recruit suitably qualified teachers.
Teenagers without C grades or higher in English and Maths will have to study for GCSEs in the subjects, but will be allowed to take other qualifications alongside them, said the Department for Education.
The English and Maths results of 16-19-year-olds who did not gain these key GCSEs will also be reported in annual school league tables, the department said.
Education Secretary Michael Gove said it was in the older teenagers best interest to remain in education to attain C grades, even if they were old enough to legally finish school.
Good qualifications in English and maths are what employers demand before all others. They are, quite simply, the most important vocational skills a young person can have. Young people must be able to demonstrate their understanding of these subjects.
According to the Department of Education, last year in England and Wales:
- Among 19-year-olds, 285,000 left school at age 16 without a C or higher in both English and Maths GCSE.
- 255,000 had still not achieved their C grade in those two subjects by the time they reached 19.
- Only one fifth of teenagers (21%) who had not reached a C grade continued to study English, while 23% continued to pursue Maths.
Teenagers who fail to get at least a C grade in their English and maths GCSEs will have to continue studying these subjects past the age of 16, ministers have announced.
Education Secretary Michael Gove said employers value good grades in these subjects above all others and that they are the "most important vocational skills a young person can have".
The reform will be introduced from the start of this term and comes as the education participation age is raised to 17, before being raised to 18 in 2015.
Currently only around one in five pupils who do not get A-C grades continue studying these subjects beyond the age of 16, according to the Department for Education.