I am isolated in a small, silent room at the back of the house, like a prisoner in solitary confinement. The blinds are drawn to shut out the hot sun. It is Saturday afternoon. Outside, my husband is sunbathing in the garden. In the lounge, my mother is sipping an iced martini while she watches tennis on television. I am not allowed any alcohol. My head is aching and my eyes hurt. A mound of paper sits accusingly in front of me on the table. There is a barbecue tonight at a friend’s house - but, of course, I won’t be going. Every summer I ask myself why I do this job - why do I assume the mantle of the dreaded examiner?

GCSE and A-level standard examiners mark a minimum of 300 scripts (mostly more) in three weeks. A strict time limit has to be imposed on examiners because of the pressure of getting results out to students in August. I spend about 20 minutes on each script, although problematic ones take much longer. I mark for seven to eight hours per day, including weekends.

The system is very rigorous and not at all subject to an individual examiner’s whim. We have model answers for nearly every question and lists of points students need to include in their essays. Assistant examiners, who are all experienced practitioners, meet their chief examiner at the beginning of the examination season to agree any dubious instructions or points. The chief examiner over-marks at least 10 of my scripts before I am allowed to continue. Any borderline or other scripts that concern me are forwarded to him for double marking, and at least one script in every 10 is scrutinised by a chief examiner. A strict quality control check is kept on all examiners by the awarding body.

So what do examiners want? The scripts I like best are those that I can read clearly. I feel a tremendous compulsion to pass this candidate, even if what she has written is inadequate.

Another script that I enjoy is the one that contains an examination howler, although I cannot award marks for this. Overseas candidates who include Americanisms are fun, like the candidate who answered a question on correct office attire as: “Ladies must never, in any circumstances, wear pants for the office.” Another amusing sentence from a UK student: “In the winter months, the farm secretary should wear nothing but Wellington boots.”

I still cannot believe the number of students who don’t seem to notice that there is a question on the last page of the examination paper. Or perhaps they have not planned their answers properly so that they run out of time. I know it is a wrench to move on from a question that a student can answer fully to another one about which she knows very little, but it must be done. Even a few notes will gain some marks. To ignore it completely is often fatal.

I feel mean about failing a candidate who has obviously learnt hisher stuff, but has not understood the question. I do wish students would spend more time reading the paper and making sure the answer they write is relevant. They should also note that most awarding bodies deduct marks for incorrect spelling of common words. An inability to distinguish “their” from “there” could lose the candidate as much as three marks in an English exam.

Candidates often send me little notes: “Dear examiner, sorry I ran out of time” (probably did not do enough revision to answer all the questions); “I don’t feel very well today” (maybe, but where is your doctor’s certificate?); “This is unfinished because my hamster died this morning and I was late for the exam” (possibly true, but you must be punctual!). I was once offered a substantial bribe by an overseas candidate, which unfortunately I could not accept.

Contrary to speculation, examiners do like to pass students. If I find a “distinction” student I clap my hands in glee and award myself a chocolate biscuit. Fortunately for my figure, the occurrence of A grade students has been rare, approximately two or three in every 100 at A-level standard.

As my husband brings me a black coffee, I make the excuse that I shun company and put up with painful eyes and throbbing head for the sake of my own students, who surely must benefit from my experience of being on the inside of the examination system. Money is certainly not the incentive - nobody could get rich from marking exam papers. Even the convivial company of fellow examiners and the free lunch each year at the headquarters of the awarding body is not enough compensation.

Of course, it’s really about power. Examiners see themselves as wielding considerable power and they also see themselves as nice people, able to cope with this responsibility. Therefore, they do give students the benefit of the doubt, they do want you to pass, so that they can be thought of as not only wise, but also kind, people. This is a personal statement - you may have other views.

Sheila Jackson is a section leader at Oaklands College, Borehamwood, Hertfordshire