A "distinction" grade is set to be introduced for A-levels, in an attempt to reward the very brightest students.

At present the highest grade is an A grade - which is now achieved by almost a fifth of candidates.

But under proposals announced on Tuesday, a higher grade - known as "A distinction" - will be introduced for the very best exam performances.

The reforms are laid out in a Green Paper which aims to overhaul the curriculum for school and college pupils, between the ages of 14 to 19.

Much of the reform focuses on allowing more teenagers to participate in non-academic, vocational education.

And the changes to the upper-tiers of A-level results might be seen as shoring up the "gold standard", when secondary school education incorporates less academic options.

The distinction grades are expected to be received by only the top 2% to 5% of exam candidates.

'Grade inflation'

The move responds to a long-running debate over the difficulty of A-levels, with some claims that the steady rise in results reflects a lowering of standards.

A decade ago, just under 12% of candidates gained an A grade, which compares with 18.5% of last year's candidates who scored the top grade.

The accusation of "grade inflation" has been repeatedly denied by exam authorities, which say that independent research has shown that A-levels are no easier than in the past.

But the stretching of the grading system will provide another benchmark by which to identify the most able pupils.

The new top grade could help oversubscribed universities, which at present have to choose between large numbers of students who are all predicted to score A grades.

Stress

The NASUWT said it opposed the proposed distinction grade at A-level.

"It will impose further stress upon pupils, which is perhaps unnecessary, and panders to those obsessed with ever-finer gradings," said general secretary Nigel de Gruchy.

"If the award is only to be given to a tiny percentage of the highest of high-flyers, it may not be worth sending such a negative message to the many other first-class youngsters now securing good A grades."