As the row over A-level results continues, Education Correspondent Lindsay Jennings looks at key questions surrounding the issue and talks to two students caught in the middle.

Q Why has Education Secretary Estelle Morris ordered an independent inquiry into A-levels?

A Because complaints about grades awarded by one of the three main exam boards in England, Oxford and Cambridge and RSA (OCR), jumped this year, while they also rose at the Assessment and Qualifications Alliance (AQA).

Some independent schools protested that their pupils had been deliberately marked down to protect A-levels from claims they have been dumbed down and become too easy.

Exams watchdog, the Qualifications and Curriculum Authority (QCA), said it would investigate how OCR awarded its grades, a move affecting 100 schools.

At that stage the QCA said it believed the grading process was ''sound''. However, as complaints from schools grew in volume and widened to include exam boards AQA and Edexcel, claims that the QCA ''coordinated'' the alleged grade fixing called into question what Ms Morris's department did or said on the matter, and when.

To clear up the mess, she asked former Ofsted chief inspector Mike Tomlinson to investigate both the grade-fixing claims and the process for maintaining A-level standards over time. ''I want to state categorically that there has been no political interference at all in the workings of the QCA and the examining boards,'' she said.

Q When did the problems at the exam boards come to light?

A When schools began to get coursework submitted for this year's A2 exams, as the second half of the new A-level is known, sent back by the boards in late August. It was then that they noticed some bizarre and apparently inexplicable anomalies in performance. Students who had gone through their careers regularly notching up A grades were suddenly getting Ds, Es and even Unclassifieds, the official term for a fail.

The drops in performance were considered even more strange because those students had done well in the same subjects at AS-level.

Q Why did the independent schools claim the QCA was responsible for putting pressure on the exam boards to cut the number of A-grades?

A QCA is the regulator charged with maintaining standards of difficulty in all public examinations. The heads, chiefly those who are members of the Headmasters' Conference (HMC), indicated that the QCA was worried that too sharp a rise in the number of A-grades awarded this year would damage the exam's ''credibility''. It then ''pressurised'' the boards into increasing the number of marks needed to get different grades.

Q If their claims are true, why have more allegations of this kind not emerged from state schools?

A They have begun to over the last couple of days. The Secondary Heads Association, which has members in both the independent and state sectors, said it has been ''inundated'' with calls from worried comprehensive heads. That has fuelled demands from some quarters for a total re-grade of all this year's A-level entries.

Q Would it not be better to do just that - re-grade every entry according to a clear system that everybody knows about in advance?

A It would cause even more chaos and confusion at this time, say opponents of the idea. Ms Morris has said most students who took A-levels this year can be ''absolutely confident that they have been fairly marked and have the right grades''. However, no one has entirely ruled out a complete re-grade yet.

Q Have A-levels been dumbed down?

A An independent international panel which examined this question on the QCA's behalf said at the beginning of 2002 that the exam system was sound, and that standards were being maintained over time.

However, that has failed to satisfy many critics, most notably Ruth Lea, head of policy at the Institute of Directors, who has said that grade inflation, the tendency to award ever higher grades, is now ''rampant''.

Their voices are loudest every August when the results come out. Ms Morris said the inquiry would look at the issue of whether A-levels have been ''devalued''.

Q But surely, if many more people can pass A-levels and get As, these days, they must be easier?

A That does not follow. Part of the confusion surrounding this issue may stem from the fact that the way grades are awarded changed in the 1980s. In the first half of their life, A-levels determined the membership of the small group who would be able to go on to university.

In those days, the proportion of entries that could be awarded As, Bs, Cs and so on was fixed under a system known as ''norm-referencing''. That meant that however well candidates performed, only a certain number could get As.

With the expansion of higher education into a mass system and a move to more modular A-level courses, norm-referencing was replaced by ''criterion-referencing''. This meant that all candidates who reached the standard required for an A got that particular grade. In theory, if everyone who took the exam did well enough, the A-grade pass rate would be 100 per cent.

The introduction of the new AS/A-level sixth form curriculum in September 2000 - commonly known as Curriculum 2000 - enhanced the positive effect criterion-referencing has on grades. Students were able to drop subjects they were less good at after the first year of sixth form and retake modules in order to get the best results.

The idea was that more people would leave school with something to show for their hard work. Independent headteachers say a form of ''crude'' norm-referencing was re-introduced at the last minute this summer to keep down the number of A-grades to protect A-levels from the claim they have become too easy.

Because of criterion-referencing, and because of Curriculum 2000, it was predictable that the number of passes and A-grades would rise this year, as indeed they did.

Q Some students may have lost places on their first-choice degree courses because they got the wrong grades. What action should people take if they think their grades are wrong and what are the universities doing about this?

A Anyone who thinks they have got an unfair grade should contact their former school, and if the teachers agree the result looks suspicious, ask staff there to make inquiries of the board that set the exam.

Universities UK said they would make every effort to help all those affected. However, at the moment, they could not give a 100 per cent guarantee that all lost university places would be reinstated because the scale of the problem was still unknown.

The Students who feel let down

Jemma Wallace was predicted to get an A in her psychology A-level. But the 18-year-old was shocked to discover that, even though she scored an A in the two exam modules, she was only awarded a D for her course work. It meant her overall grade came out as a B.

The former pupil of Yarm School, Teesside, still managed to secure a place at Newcastle University to study for a business management degree with her added A in Business Studies and C in Biology.

But she said it did not remove the anger she felt at the exam system, in which she has now lost confidence.

"When the results came out there were a lot of tears," she said. "I'm lucky in that I'm at the university I wanted to be at. But it does make me feel really angry and disappointed.

"This whole thing is going to affect younger students who will think why work so hard for something when you're not going to get the marks you deserve."

Huw Miller was told to expect an A/B in his psychology course work. But when the results came out he was left staring at a U for unclassified. His overall grade was an E.

"I was really shocked," he recalled. "But as I started talking to other people I realised they had the same problems."

Huw, 18, a former pupil at Yarm School, Teesside, was accepted for his chosen course at Northumbria University - a four-year product design and technology degree.

But he said he felt anger towards the exam boards and, although he had secured a place at university, still wanted a good grade in psychology.

"I think it's terrible that the exam boards have done it - it's people's lives they are changing and some haven't even got into the universities they wanted.

"It doesn't give you much confidence in the system."