Since their launch, GCSEs in most subjects have been not one, but a series of exams, strictly divided to cater for the abilities of all the children who take them. There is one exam for the As and Bs and yet another for the Ds and Es.
An inquiry launched this summer by Government exam regulators will look into claims that the divide, known in the jargon as "tiering", will undermine the drive to raise standards at GCSE. The Qualifications and Curriculum Authority is hoping to make proposals for reform in time for the revamped National Curriculum which will be introduced into schools next year.
Advocates of the tiering system say it was set up to ensure that exams provide for children at the bottom end of the ability range, but can still be challenging enough to be meaningful for those at the top.
Its critics say that the tiers undermine efforts to maintain standards, demotivate children, and represent a system of selection by stealth.
While most subjects at GCSE are divided into two tiers, maths has three. Teachers must decide, sometimes when children are as young as 14, where they fit. If they are put in for the top tier of exam, they can aim for an A*, A, B, C or D. If they are deemed more suitable for the lower tier, a B is the best grade they can hope for.
In theory, teachers can wait until the month of January before their students take GCSEs, helping them to decide which tier would suit them best. But in practice, much of the assessed work they do in the first year of their course has to be geared to one tier or another.
Most teachers support the idea of splitting at least some subjects into papers geared towards different ability groups. What many oppose is the detail of the way the system works in practice.
The problem is that children can only go in for one tier at a time. If you go in for the lower tier, you cannot get more than a B. If you enter the higher tier and miss, you run the risk of ending up with an ungraded mark for your efforts.
Overlapping grades allow candidates to gain the same grades on different tiers of the exam, a system designed to act as a "safety net" for those who do better, or worse, than their teachers had expected.
Mathematics has provoked by far the greatest controversy. Unique among subjects, it retains a three-tier set-up which makes a severe cut off between grades.
Top tier candidates can get an A*, A, B or a C. If you miss the C, you get a U. Entrants to the intermediate tier cannot better a B, while those who take the bottom, (foundation) tier, are thereby condemned to a grade no better than a D.
"It's a crazy system. It makes no sense to me at all," said David Burghes, professor of education at the University of Exeter and an expert on maths teaching. "It's such an unsatisfactory, unfair system.
"It will lower expectations, because teachers have to play safe and enter kids for the intermediate tier.
"I oppose the tiering system on principle because you can get a grade in two different ways. You can get a grade C in maths on two papers and it is easier to get it on an intermediate paper than it is on the higher paper.
"The advantage of O-level and CSE papers was that you could do a double entry," said Professor Burghes. He advocates a system of extension papers; a basic exam for all candidates and extra papers for the higher grades.
Others question the need for any tiering in many subjects.
John Dunford, general secretary of the Secondary Heads Association, said: "There would be a general view that there is very little logic about the tiering arrangements over all the subjects.
"To have one kind of tiering in geography and another arrangement in maths makes no sense at all. We would have expected the awarding bodies to produce papers that were differentiated by outcome rather than by the questions they ask.
"They have gone too far with the tiering - it simply threatens to return to the days of the O-level and the CSE."
The Tiering Structure
MOST MAJOR GCSE exams are split into two parts. Teachers can choose to put their pupils in for a "foundation" tier, covering the grades from C to G, or a "higher" tier, covering the top grades from A* to D.
Exam papers for each tier are pitched at a level appropriate for the grades that they cover. Lower tiers are designed to give opportunities for the less able students, while higher-tier exams prompt stronger candidates to give greater depth to their answers.
Maths stands alone in having three tiers: a foundation paper covering grades D to G; an intermediate tier covering grades B to E; and a higher tier covering the top grades, from A* to C.
Some subjects, however, are assessed with a single exam. Exam regulators believe that some subjects - including religious studies, music, art, history, PE and performing arts - can be assessed with a single test that covers the entire ability range. The exams are designed to overlap, but pupils cannot take more than one tier at the same time. Those students who fail to gain the bottom grade for their tier are marked ungraded.
Teachers must decide which pupils they enter for which tier some six months before the exams are actually taken, although it is possible to make late changes.
Advice to teachers makes it clear that the nature of coursework for each subject will vary from tier to tier.
The syllabuses themselves remain the same in most subjects, regardless of which tier the students eventually go on to take.
Should You Really Try Again?
SCHOOL LEAVERS who miss the grades they expected at GCSE face a complicated set of choices. Experts advise them to consider carefully whether they need to resit exams.
In some cases, students can secure a place to do A-levels, AS-levels or advanced and intermediate GNVQs without them. Alternatively, school leavers could choose one of the new "part one" GNVQs, which are set at the same level as GCSEs but designed as a work-related alternative.
If students decide to try for better grades, they can sit exams either in the winter, or spend a year brushing up and sitting the exam in the summer. Those who take modular GCSEs may have the option of retaking some modules after they get their results. In the modular maths course, for example, the final module, which covers the entire two-year course and is worth over 60 per cent of the marks, can be retaken.
Some colleges allow students to retake exams alongside an A-level or other course, or will accept them straight on to a vocational course. But the record for students who do try again is not good. John Dunford, general secretary of the Secondary Heads Association, says: "Other than in maths and English, most headteachers would advise students not to spend too much time retaking GCSEs they have failed, but to move on in their career. They find it hard to motivate themselves and the results aren't good."
George Turnbull, of the Assessment and Qualifications Alliance, says that the post-exam period is "a time to reflect, but it might not be a very comfortable time."
Examinations: How Did You Fare?
A SELECT band of school-leavers will have a chance to pick over their GCSE scripts for the first time this year, under a government scheme designed to make the system of exam appeals clearer. Students at 200 schools will be able to see their exam answers under a pilot project. Ten thousand A-level students had the same chance in the first stage of the scheme last week.
The scheme aims to make exam marking and appeals more transparent. But it is unlikely to lead to an explosion in the numbers who challenge their grades. Students in Ireland who saw their scripts in a similar scheme were so amazed by their errors that the number of appeals went down. Last year there was a total of 14,923 appeals involving 29,129 candidates - schools can lodge an appeal on behalf of more than one candidate.
A new Examinations Appeals Board will run the system, but any appeal must be made initially to the board that set the exam. Candidates who want to challenge grades must have the support of their school, who will send appeals to the board. Schools can ask for a check of the examiners' arithmetic to ensure that marks have been added up correctly, or they can request a re-mark. Boards can raise the grade, but they will not be able to lower it.
The process is expensive for schools, which can ask for a remark, a re- check or a re-mark with a full report. The re-check alone costs pounds 9.30 for one GCSE. If you are not satisfied after this, you can apply to the board's appeals secretary.
And if you are still dissatisfied, you can at this point appeal to the independent appeals board.