Independent schools are poised to abandon GCSEs because, they say, the exams have been dumbed down to meet Government targets.
David Vanstone, chairman of the Independent Schools Association (ISA), said the Government's refusal to replace GCSEs and A levels with a diploma system had left schools "in limbo".
Many independent schools are on the brink of deserting GCSEs and teaching 14 and 15 year-olds AS levels to stretch bright pupils, he said.
Nearly 600,000 teenagers are due to receive their GCSE results on Thursday, with experts predicting that the numbers scoring good grades will rise again.
Head of the 300-pupil North Cestrian Grammar School in Altrincham, Mr Vanstone said GCSE coursework in particular was "stultifyingly boring" and open to cheating.
Mr Vanstone said: "We have got the problem that the maths exam in particular is being made less challenging to make sure people get up to pass standards.
"The Government is struggling - it is keen to promote an increasing pass rate in both English and maths at GCSE to indicate that progress is being made but it isn't really managing it."
He added: "One of the problems for the most able people is that they can get to the top grades sometimes as much as a year in advance.
"To move ahead at the pace they should go, people are going to need some further or more difficult tests," he said. "We are getting close to the point now where the bold steps will be made to try to move forward," he said. "Schools may get bold to the point of actually ditching GCSEs altogether in some subjects."
In 2003 Eton College announced it was to bypass the GCSE examination and go straight to AS level.
But many public schools that were frustrated with GCSEs were prepared to wait for a Government review of secondary school qualifications chaired by former head of Ofsted Sir Mike Tomlinson.
The independent sector supported Sir Mike's plans for replacing GCSEs and A levels with a new diploma system that combined both academic and vocational courses.
A Labour spokesman said: "GCSEs are tried, tested and trusted and as (Schools Minister) Lord Adonis made clear this week, rises in performance are thanks to improvements in teaching and the hard work of pupils.