By Justin Parkinson BBC News Online education staff

A-levels are very stressful for thousands of students each year

Pass rates have improved for every one of the last 22 years, so much so that this summer more than one in five exam entrants got a grade A.

Some think A-levels are becoming easier; others that teaching is improving.

Irrespective of this, leading universities say they are struggling to decide between thousands of highly promising candidates.

A working group on 14 to 19 year olds' learning has proposed a way to differentiate between the merely bright and the very brightest.

It suggests creating new, elite grades: the A+ and even the A++.

'Stress'

Gifted students could answer extra questions at A-level, designed to test them more fully.

But is the old exam so bad?

A group of highly able students at Allerton High School in Leeds had some mixed views about its effectiveness and its future.

You have to differentiate in some way Tom, 18

Sarah, 17, doing art, English and history, said: "If you are at the bottom of the current A-grade band, I suppose you wouldn't want the A+ and A++ grades to come in.

"It would mean more pressure for people looking to go to university."

Roy, an 18-year-old science and maths student, said: "If you divide the A grade, most of the universities are going to look at whether you have got between 85 and 90% in an exam.

"It does seem that that puts a lot of stress on just a couple of percentage points, which might change depending on how a student does on a given day."

Students who complete A-levels are already given a numerical breakdown of their exam performances to go with their grades.

So, one might get an A with 92% and another with 85%.

'Would make sense'

This information is not, however, made available to universities.

Might it not be better just to give them this, rather than tell students they need an A++ to stand a chance of admission?

Every system is going to have its faults Carly, 17

Tom, 18 and studying sciences, said: "It would make sense to have the 20% or so who get an A grade divided.

"You have to differentiate in some way. But universities have to get it right as well. That's in everyone's interest."

The working group's plan for a four-part diploma, covering all abilities from 14 to 19, would not come into being for up to 10 years.

Carly, 17, studying history, English and politics, said: "Every system is going to have its faults.

"For lots of universities you've got 10 people applying for every place. Universities are seeing lots of A-grade students.

"They are looking for something to set good applicants apart. At the moment there's no way for them to do that."

Of course, universities also look at teachers' comments and general reports. Cambridge even asks for a numerical breakdown of 17 year-olds' first-year A-level (AS-level) results when considering them.

Some, such as Oxford, Cambridge and Durham, interview all candidates, but for most others that is not possible, due to pressures of cost and time.

'Dumbing down'

For bright students it can seem a lottery.

The government considers it tantamount to blasphemy to criticise the increase in high-grade A-level passes as evidence of "dumbing down".

Part of the reason for the phenomenon is that, until the early 1980s, a quota system was in force.

Only a certain percentage of A-level exam entrants, however good, were to be awarded an A.

The Conservatives have proposed reintroducing something similar.

The proposals are not revolutionary Julie BrownRigg, teacher

To the students at Allerton High this was an abhorrent idea.

Tom said: "If that's what they want to do, they must be ignorant of what's going on."

Julie BrownRigg, head of the 200-student sixth form at Allerton, puts the rise in grades down to improvements in teaching, which gives students a "more sophisticated" way of looking at subjects.

The rise of the national curriculum since the late 1980s, she adds, has given children a better factual knowledge by the time they are 16. A-level teaching has, as a result, looked more at developing "analysis".

Mrs BrownRigg said: "The proposals by the working party are not revolutionary. They leave as many questions as they provide answers.

"But we definitely don't want to go back to the system where only a certain amount could get a top grade, no matter how well everyone did."

Amid all the talk of the A grade "failing" the brightest, critics tend to forget an Advanced Extension (AE)-level already exists.

As with those who could one day be aiming for A+ and A++, candidates are asked more stretching, in-depth questions.

Mrs BrownRigg said: "It is something which could be used more by universities if they wanted to."

Some law and medical schools, overrun with high-quality candidates, have started setting their own aptitude and intelligence tests.

Ambitious A-level students are already having to jump through more hoops than a circus dog.

But how much can a university really know about a candidate before they arrive, no matter how sophisticated the testing regime?

As Roy said: "We can only talk about the exams we are doing. How could we know whether a system will work or not?"