SOUTH Devon head teachers have launched an attack on the Government for 'moving the goalposts' in English GSCE papers.
Teachers said hard-working students lost out on higher grades because exam papers were marked too harshly.
The changes — which many claim are politically motivated — had a devastating impact, particularly for those on the C to D boundary.
Education leaders have complained that exam boards substantially increased grade boundaries, leaving pupils with lower results than expected.
Although schools locally performed better than before, they say the benchmark shift still had an impact.
Exam chiefs admitted that grade boundaries had changed, but insisted standards have been maintained in line with previous years.
A group of 28 Devon schools has now joined the national outcry over GCSE English marking which have seen schools' results drop 10 per cent.
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.
Under new targets 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 English and maths,
While many South Devon schools bucked the national trend, the impact of the adjustment was still felt.
Cathy Gilfillan, head teacher of St Cuthbert Mayne school in Torquay, said: "The tasks and criteria were almost the same as last year with no variation of the task difficulty, but grades have been changed.
"Eighteen of our students, which is about 10 per cent of our cohort, would have received C grades but received D grades instead.
"We are suspicious that this is politically motivated to depress the number of C grades in English.
"There is no appeal possible because it was not an exam but a task.
"I am frustrated and angry about this inexplicable shift of the goal posts on behalf of our students."
South Dartmoor Community College's principal Hugh Bellamy agreed: "Children have met the criteria but, because of the change, not got the grades.
"Our young people who worked so hard for so long have been treated with utter contempt."
Vyv Game, the headteacher of Teign School in Kingsteignton, said: "The lack of consistency in the marking of English is frustrating as it makes predicting outcomes very difficult from one year to the next. Any attempt to increase the difficulty of examinations has to be done gradually so that the impact on individual students is minimised."
Glenys Stacey, chief executive of exams regulator Ofqual, defended the changes saying: "What we have done this 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."