There’s one line that invariably appears every year in RTÉ's coverage of the Leaving Certificate results; it’s the kind of line the media doesn’t much like, because it’s a dampener, downplaying the story, but it’s an important one; "this year’s results are broadly in line with previous years".

Amid the inevitable public commentary that surrounds the issuing of the results every August, on the airwaves and in the newspapers - the parsing of Maths results, of failure rates in this or that subject, this is a point that should not be forgotten. Year on year, there’s no big change in the results students are awarded. It’s an important and reassuring feature, and it’s no accident.

For an exam like the Leaving Certificate it’s vital that standards are consistent. The results of a student who sits their Leaving Certificate this year have got to be comparable to those of someone who sat the exam the year before, and the year before that. Like has got to be compared with like, otherwise students sitting an exam in one year as opposed to another could have an unfair advantage, if a paper was easier or harder.

But how is this achieved?

The marking of papers is a complicated business:

- Before the exams take place a marking scheme is devised for each paper, awarding scores for each question, and each part of a question. But this initial marking scheme is just a draft.

- After an exam takes place a senior examinations team analyses a selection of scripts. They consider any issues that may have been raised by teachers and other professionals, and at this stage they may make preliminary adjustments to the draft marking scheme.

- The examiners - in the main teachers - who will be correcting the papers are then trained in the application of this marking scheme.

- Each of those examiners then begins by correcting a sample selection of the papers they have been assigned to assess - it’s usually about 6%. They send those scripts back for monitoring and review.

- Here’s where the standardisation really kicks in; if the results from this aggregate sample of papers does not tally with the results of previous years - if these results are noticeably better for example, or worse - then a subject's marking scheme is adjusted again. This, usually final, marking scheme is then applied across the board.

- Additionally, if the marks being awarded by any individual examiner are out of kilter with the rest, if an examiner is awarding an unusual amount of high scores, or low scores for example, then this too is examined and addressed.

There are other factors that can lead to changes in the results that students achieve year on year.

Last year for instance, there was a fall in the proportion of candidates getting higher marks on some Ordinary Level papers, and a corresponding rise in the proportion of lower marks awarded in some Higher Level papers.

That’s because more students opted to sit Higher Level papers in those subjects. So a student who might have received a 1 in Ordinary Level Irish - had they opted for that paper - may have received a 5 at Higher Level instead.

The aggregate Leaving Certificate figures that RTÉ and the rest of the media will pore over and analyse tomorrow are just one aspect of the story though.

What this week is really about are the tens of thousands of individual stories; every single Leaving Cert student, along with those who love and support them, has their own story. And the Leaving Certificate is just one small chapter.