It’s like the fall of Saigon. Everyone knows it’s over, but we have to act as if things are normal and we’re still in control. It’s just a few weeks until the end of the year and, like the American ambassador scrambling for his helicopter, everyone - kids and staff alike - is waiting for the order to evacuate.

Hierarchies are breaking down, the old order crumbling. A maths GCSE exam is abandoned when one candidate sneaks out to the girls’ toilet and sets fire to the sanitary towel bins. A Year 11 gang hijacks a school bus and takes hostages: they demand pound;500 from petty cash and safe passage to the nearest McDonald’s.

Most members of staff simply shrug and take refuge in the staffroom, bickering among themselves about the cover list. But some diehards, led by John Baller, insist on doing their final tour of duty in the corridors, where the strip lights flicker threateningly and the sound of drum and bass echoes through the gloom. John leads reckless missions into the Year 11 common room, ordering hooded tops to be lowered, fake Christian Dior earrings to be handed over, ipods to be turned down. “Come on you little bastards,” he screams, “let’s have some respect!” He mutters something about reprisals and sends every fourth kid to the referral unit.

It’s no better at the school entrance, where parents have become as hysterical as their gate-happy offspring. Yesterday a council surveyor taking photographs for a road-widening scheme was set upon by a screaming mob who accused him of being a paedophile. Eventually he was cut down from the railings, but not before a group of photographers had arrived to cover the story.

For those who prefer their dramas to be more constructively channelled, the annual school production is in rehearsal. Orlando Jones, head of drama, is producerdirector as usual, but surprisingly he’s been joined this year by Cynthia Thyme as scriptwriter and Harry Thomas, who’s agreed to write the score. Cynthia has come up with a Brechtian, gender-ambiguous adaptation of South Pacific, set in Guantanamo Bay and with some of the some major numbers reworked. She’s particularly pleased with “There Is Nothing Like a Class-Conscious Dame” and “Happy Talk Costs Lives”.

Cynthia and Orlando don’t always meet eye to eye artistically. Orlando finds elements of Cynthia’s version too didactic. She finds his sexism unacceptable, particularly his insistence that the chorus line of Year 12 girls should wear grass skirts and coconut-shell bras. As for Harry, my very own leading man, well, something doesn’t seem right.

I find Harry in the music room playing a mournful rendition of “Younger Than Springtime” on an ancient piano. He looks up and smiles and I ask him if he wants to go away on holiday when all this is over. “Just you and me, Harry. It’ll be lovely.” Then he tells me. He resigned at Easter and he’s going to Kerala to “find himself”. He organised it all before we got together and didn’t tell me because... his voice trails away.

Then he jumps up and says why don’t I go with him. But I’ve missed the resignation deadline, and the boat generally. I kiss him on the cheek and go home. That night I fall asleep among a pile of unmarked history projects, the melody of “Bali Hai” playing in my head.

Charity Casement is the alter ego of a north London teacher. Next week: Is this the end?