Reforms to GCSEs and A-levels will amount to nothing more than "houses built on sand" if the Government fails to tackle "shocking" failings in the way exams are marked and grades awarded, heads of leading independent schools have warned.
Proposals to overhaul public examinations announced by the Government are welcome but are almost certain to be undermined by long-standing problems such as poor quality marking and unsatisfactory awarding of grades by exam boards, said a report by the Headmasters' and Headmistresses' Conference (HMC).
The organisation detailed what it claims are failings in the "examinations industry" in England, including "inexplicable inconsistencies" in awarding of grades, "erratic and inconsistent" marking and an obstructive approach to appeals between 2007 and 2012.
Schools have received "unexplained" and "very large" variations in the percentage of grades given to successive years of pupils in the same GCSE and A-level subject, in spite of the subject being taught by stable teams of staff to students of similar ability, the report said.
The HMC added that exam boards were too secretive in their approach to challenges from schools with the appeals process, allowing the boards to "hide behind protocol" rather than account for poor marking.
The organisation, which represents the heads of 221 schools in England and a further 31 in the rest of the UK, said many of its members had "voted with their feet" in the face of the problems, with a surge in members opting for international GCSEs.
"Every year many thousands of students in England are awarded the wrong grade in one or more of their GCSE or A-level examinations. And every year schools and colleges are faced with diverting resources into correcting this problem," the report said. "This arises in the main from a fact that all of the main examination boards concede in private - the quality of marking is not good enough."
Christopher Ray, high master of Manchester Grammar School and chairman of the HMC, said: "The state of the examinations industry is truly shocking and is clearly no longer fit for purpose. The problems go far deeper than this year's disastrous mishandling of the English language GCSE grades. We are publishing this evidence today on behalf of all students in state and independent schools in England who do not receive the marks or grades that accurately reflect their performance and achievement."
Education Secretary Michael Gove announced last week that GCSEs are to be replaced by a new English Baccalaureate Certificate in secondary schools in England. The new-style qualifications, to be known as EBaccs, will do away with the "modules" which allow GCSE students to retake parts of their course, cut back heavily on the use of classroom assessment and coursework and return to the emphasis on a traditional end-of-year exam.
A Department for Education spokesman said: "We have been clear that the exams system is in desperate need of a thorough overhaul. That's why we are consulting on EBCs, new, more rigorous exams for 16-year-olds, and why we are reforming A-levels, with universities and employers responsible for their design. We agree with HMC that there are serious problems with marking and quality control."