The number of teenagers failing their GCSEs will soar as a government drive to raise standards makes the exams harder, education chiefs have warned.
Candidates will not be awarded a C grade or better unless they pass new "functional skills" tests in English and maths under moves designed to ensure pupils master the three Rs.
But England's biggest exam board - AQA - warned a generation of teenagers would suffer a "grave injustice" when GCSEs become more difficult as a result.
Pupils will struggle to compete for jobs and university places against school-leavers who achieved better grades in previous years, the board said.
AQA deputy director general Andrew Bird said the functional skills tests would effectively "change the standard" of GCSEs.
"From our modelling, it will suppress the pass rate at A*-C at GCSE," he said.
This suggests that many pupils currently achieve Cs without mastering what the Government believes are "the basics" of literacy and numeracy.
In written evidence to the Commons schools select committee, AQA said reforms were "a major concern".
The significant "change in GCSE standards" in English and maths would distort school league tables, the board said.
