As GCSE results were published today, a row erupted over the marking of this year's English exams.
Concerned teachers suggested that this summer's papers were marked too harshly, with a number of schools reporting unprecedented numbers of fails among their pupils.
English teachers, who received breakdowns of marks yesterday, ahead of today's results, complained that exam boards had substantially increased grade boundaries, leaving pupils with lower results than expected.
Exam chiefs admitted that grade boundaries had changed but insisted that this often happens and that standards have been maintained in line with previous years.
Brian Lightman, general secretary of the Association of School and College Leaders (ASCL) said the union had received a “large amount of feedback” from “dozens and dozens” of schools.
He said: “The grade boundaries in English have been moved up, on the C/D borderline, and they've been moved up very substantially.”
Mr Lightman said he understood that in some cases, boundaries had been moved up by “10 or 18 marks”.
He likened the situation to “a hurdles race in the Olympics and the athletes have just left the ground to jump over the hurdle and it's been raised”.
New GCSE English courses have been introduced and are being awarded for the first time this summer.
Pupils now take GCSE English, which includes some English Literature, or English Language GCSE and can sit another one in English Literature.
This year's national results show that in the English GCSE, 63.9 per cent of entries got at least a C, compared to 65.4 per cent last summer, while 15 per cent were awarded an A or A*, down from 16.8 per cent in 2011.
In English literature, 76.3 per cent of exams were awarded A*-C, compared to 78.4 per cent last year, and 23.2 per cent got at least an A, against 25 per cent in 2011.
Exam chiefs said that the falls were partly down to more candidates switching from taking the subject early in the winter exam season.
They said that historically, there had always been significant numbers of re-sits after the winter exams, and that the winter season tended to produce lower results.
As more students move to take their English exam in the summer, this has an impact on results.
Referring to concerns about English grades, Mark Dawe, chief executive of the OCR exam board, said: “Our job is to maintain the standard of a qualification year on year and in Englishthat has been done. The standard and the results overall have been maintained.
”There have been some challenges and discussions over the last 24 hours about boundaries, but those boundaries do move, unit to unit, they do move, session to session, but the overall judgment of the examiners and the quality of the students' work is key here, and those boundaries sometimes have to move to ensure that's delivered.“
Ziggy Liaquat, managing director of the Edexcel exam board said: ”We do understand that students and teachers not getting results they anticipated is unsettling.
“But I think the key point is we base our decisions on the quality of the work that we see in front of us. We use other data points to do this in collaboration with the regulator, so at qualification level, students should be reassured that they've got the grade that their work merits.”
He added: “Absolutely, grade boundaries at unit level do change and have changed historically and have changed again this year, and that's especially the case when you have got a new specification that's settling down and that's what we're seeing this year.”
Mr Dawe said examiners are “very comfortable with the overall grades they've been awarding to those students”.
Mr Lightman also raised concerns that the fall in English grades will have an impact on schools meeting the Government's floor targets.
Under new targets, which apply to today's results, schools will be considered failing if they do not ensure that at least 40 per cent of their pupils get at least five Cs at GCSE, including Englishand maths (up from a 35 per cent target last year) and have a below average percentage of pupils making the expected progress in these two core subjects.
“A large number of schools have had a serious effect on their five A* to C with English and maths indicator,” Mr Lightman said.
“It doesn't take a genius then to conclude that some schools are going to have a big problem with the new higher floor standard as a result of that.
”What it would appear, from what we're seeing here is that standards of achievement haven't changed one iota in those schools, it's just the way the marking has been changed this time round.“
Glenys Stacey, chief executive of exams regulator Ofqual, told the Today programme: ”Our job is make sure exam results are right. What we have done this year, and last year, is to hold the line on standards steady.
“If the qualification and the type of student is broadly the same, then results will be broadly the same.
”Any difference in results in English or other subjects will reflect differences in the make-up of the group taking the exam, in terms of the numbers or their abilities.
“This year we have seen, in English, differences in both the qualification itself and the students taking it.
”Having said that, I am not expecting to see a 10 per cent reduction in English results across the board.“
A Department for Education spokesman said: ”Ofqual's job is to maintain exam standards over time and make sure that students get the grade they deserve. Our job is to drive up school performance. We judge each school on a case by case basis but we make no apologies for setting high expectations and will not hesitate to step in where there is evidence of chronic under-performance.
“We've brought in a tougher but fairer floor standard. Tougher - because it is right that minimum expectations of schools should continue to rise. Fairer - because it will reflect that many schools take children with low levels of attainment and do a good job of bringing them up to standard.”
Janet Parkinson, head of English at St Mary's Catholic High school in Astley, Greater Manchester, said pass rates were not as high as they expected.
She said: “About 30 of our students went from C to D. They have raised the bar that's needed to get a grade C.”
Miss Parkinson said she thought it was being done to deal with the perception that exams were getting easier.
She added: “They have done it, I think, as a political move and it's very unfortunate for students who are in this year's crop.”
Danny-Joe Parkinson, 16, received a D in English language and had been expecting a C. He plans to resit the exam.
“It's just that it's going to cause me problems. It's going to cause more work for me. It does get on your nerves a bit but I should have been good enough to be well within that C anyway. What it comes down to is I didn't try hard enough in my revision.”