Sometimes the decision to appeal is straightforward. If results across a whole subject are disappointing, it’s an indication that something may be amiss. With all the data we have now, it’s possible to predict exam grades accurately, particularly at a school like ours, which has a settled staff.

You get a feeling for how each department is likely to fare. If results are out of line with expectations, we will ask for a re-mark.

Individual cases are more difficult. There’s been a lot of publicity about exam boards getting things wrong; as a result confidence in the system has fallen. For many pupils and their parents, the knee-jerk reaction to a disappointing result is “there must be a mistake”, when, of course, it may just be that the candidate didn’t perform to the best of his or her ability. But when people see someone being marked up from a D to an A* they begin to think “what if?”. And not just pupils. Our head of history, after the AS papers were regraded, told me he couldn’t help wondering what might have happened if we’d asked for the other two modules to be re-marked as well. Ten or 15 years ago that wouldn’t have happened; teachers were deferential towards the external exam procedure, and grades were accepted at face value.

It’s unfortunate that people have less confidence in the marking process than they used to, but the move towards accountability and openness is good. Being able to ask for exam scripts back has been a big step forward.

These scripts are a wonderful tool for professional development. We can see exactly what pupils have written, which may be very different to what their teacher would have hoped for, and we can check that the marking process has been carried out correctly.

The exam system isn’t perfect, but it works well most of the time. If we were to move towards everything being marked by schools, there would be more potential for dishonesty. At least with external examiners you know that any failings are likely to be genuine mistakes, and it’s good to have that element of impartiality. It’s also worth remembering that exams can be over-marked as well as under-marked. Do schools appeal if results are better than expected? I think usually it just goes down as a pleasant surprise.

The increased number of appeals is also a result of students becoming more skilled at playing the exam game. At AS level, where they know the marks will be carried forward, candidates will perhaps see that they are just a few marks away from a grade boundary, and decide to push for the extra marks by having a module remarked or by re-taking it the following January.

It’s an understandable approach, given the importance of these grades in making university applications.

Ultimately, it’s up to pupils and their parents to decide whether or not to appeal. We provide the necessary forms, and the only extra work involved for the school is to sign the paperwork when it’s complete. But we will always give a professional opinion, and sometimes we advise candidates that they may be better off accepting their grade. We have had cases where an appeal has led to a lower mark, rather than a higher one and, while some candidates get moved up, a majority of appeals bring no change to the results.

On the other hand, there are times when a teacher will push for a re-mark, even if the pupil isn’t too bothered. The boy who had his religious studies paper moved up four grades was an unassuming person, and was willing to put his result down to a bad day. It was his teacher who insisted it might be worth pursuing matters. It was a good job he did.

Tim Gartside is headteacher of Altrincham grammar school, Trafford. He was talking to Steven Hastings