They say the Midland Examining Group has reduced results for pupils throughout the south of England by up to three grades. And they claim the biggest reductions have been made in schools where new teachers have taken over the subject.
Sue Moseley, head of textiles at the Vyne School in Basingstoke, was shocked to be told in the summer that all 16 of her pupils taking the Home Economics: Textiles exam were to have expected results reduced by the equivalent of at least two grades.
The worst affected pupil had her coursework marks cut from 167 to 114 which meant her final grade was reduced from B to D. Another girl had her grade cut from a C to an E.
The Cambridge-based examining group, one of six members of the Joint Council for the GCSE, has told the schools that it will meet teachers individually but not all together.
Mrs Moseley, who has taught GCSE textiles for several years and has never complained before, said: "All 25 schools I have contacted so far, most with long experience of this exam, say their marks have been unfairly reduced.
"There is a remarkable similarity in the comments made in the reports on coursework and for some reason the reductions are expecially severe where there is a new teacher taking the subject, or in schools taking the exam for the first time with this board.
"We have suggested that we all go to the Midland Examining Group and talk to them, but they insist on every case being dealt with individually.
'The problem with that is that we need to compare marks at all the schools. "
Felicity Higgins of the Thomas Hardy School in Dorchester said all but a handful of her 65 pupils had their coursework cut by 23 marks and went down one grade.
"We have followed the assessment procedures laid down by the syllabus on the basis of many years teaching the subject, but the examiner seems to have suddenly required all sorts of things we didn't know about," she said.
"We were very surprised to find there seemed to have been a change in the rules and it has happened at many schools."
Dr Ron McLone, chief executive of MEG, said he would review the complaints and would not rule out meeting the schools.
He said: "I recognise that these schools are expressing concern. It may be that they have changed syllabuses and that staff may not have sufficient experience of the different assessment criteria involved. " * The Southern Examining Group has admitted that GCSE English papers from pupils at two schools in Swindon were wrongly awarded lower grades than expected. All 202 papers at Kingsdown School and a sample from Bradon Forest School are being remarked.