Summer exam time is the single most stressful time that the majority of pupils will encounter during their school days - and they have all my sympathy.
From the moment the first public exam starts, the atmosphere in the library alters dramatically. Gone are the boisterous youngsters, exuding energy as they thump each other jovially in passing. In their place come tense, snappy adolescents with spotty complexions and dark shadows beneath their eyes.
Each morning they arrive early for some precious last moments of cramming before their exam begins. Then, at about 10 or 11 o'clock, a second wave arrives, whose exam is after lunch. They have slightly more time on their hands and tend to want to work in groups, testing, checking, arguing and comparing notes. They work fast, almost manically, and tears spring readily to their eyes at the slightest provocation.
As lunchtime approaches, you can see them grow lightheaded; the sensible ones begin to scoff chocolate and high-energy drinks surreptitiously, but I would never stop them eating at a time like this. The others spurn a break in favour of more 11th-hour cramming although you can almost hear the information bouncing against their brains and ricocheting off. They have done enough. If not, it's too late now.
I move quietly between them in the stifling heat, opening windows, switching on fans, attempting to answer panicky questions about the French subjunctive and trying to persuade some that at this stage a run around the block would do them more good than anything else.
"Oh shit, my pen's broken," sobs one girl. "I might as well give up now."
"I'm going to be sick," says another. And is, quite tidily, into his carrier bag.
They infect the others, and as the exam moves closer the atmosphere becomes slightly hysterical.
The library at lunchtime is not just for the sixth formers, of course; it is for the whole school, and there are plenty of younger ones riding on the back of this hysteria and trying to wind up the poor exam candidates.
"Why's he being sick? That's disgusting."
"Miss, their books are everywhere - there's no room for our stuff."
"How come they're eating chocolate. You sent me out when I had that Flake last week. It's so unfair."
Yes it is, but it's called discretion, and all I can do is point out that the same courtesies will be afforded to them when their turn comes.
Exam season only lasts a matter of weeks, after all. I don't think many of them could stand the pace if it went on for much longer, but somehow they stagger through, buoyed by the thought of imminent trips to Ibiza.
Parents tend not to see their teenagers studying because they are in their rooms, and teachers don't see because they are actively teaching them.
But in the library, I do see them engaged in quiet study, hour after hour, day after day. And when I hear the accusation that exams now are easier, I think of those hours and those days, and I know that for most pupils who get a good exam grade, it's because they have worked their socks off.
All credit to them.
Claudia Court works in the library of a London secondary school.