GCSE results may face a major overhaul that could result in a cut in the number of grades available, it was suggested on Friday.
In a new report, the exams regulator indicated that it was time to look at whether GCSE grades should still range from A*-G.
It opens the door to reducing the number of grades awarded to students.
New GCSEs are due to be introduced in 2015, so a new grading system could be tied in to it.
Ofqual's new corporate plan, setting out its aims for the next three years, says: "Before we implement new GCSEs to match the new national curriculum, we will review the way in which GCSE results are reported so that they best meet their intended purposes.
"The grading structure stretches from A* to G, and it is time to look now at whether this is how it should be."
It is understood that reducing the number of grades available could be one of the options considered.
Professor Dylan Wiliam, Emeritus Professor of educational assessment and the Institute of Education said: "I think that changing the system is a good idea, but reducing grades is a mistake."
"What would be more appropriate to have is a percentage score with a measurement error," he suggested.
Under this system, students would get a mark between nought and 100, along with a given margin of error.
For example, a candidate could score 60% plus or minus 15%.
"The public would understand that," Wiliam said.
He said that part of the problem is that current GCSE grading is the legacy of a system introduced 50 years ago - the old O-level and CSE exams.
Under that system O-levels were graded A-C, and CSEs were grades one to five.
A grade one was equivalent to an O-level grade C, with the others equal to grades D-G.
"In those days a grade F was the national average in the CSEs."
Professor Wiliam said that as GCSE achievement has gone up, because exams have got slightly easier and pupils are working harder and getting bright, the lower grades, from E-G have become squeezed out.
"The problem is, we are not honest about the inaccuracy of assessment," he said.
He added: "GCSEs are becoming increasingly irrelevant in a three to 19 education system.
"If kids have got to stay on, why do we need these expensive examinations?
"Schools spend more on examining kids than they do on books and paper."
Last summer, nearly one in four (23.2%) GCSE entries scored at least an A grade while almost seven in 10 exams (69.8%) were awarded a C or above.