Nigel Horsmel, the acting head, has ruled that all NQTs should be observed in the first week of every term. He says it’s to keep us sharp, to stop us going flabby in the holidays. So I spent most of the Easter break preparing a Year 8 lesson on paganism in Celtic Britain. This is a rather transparent attempt to get on the right side of my mentor and observer, Sandy McSniff, a hippy who has a miniature stone circle laid out on her office floor and who blames any mishap that befalls her on the fact that St Brian’s was built at the intersection of five ley lines.

As I stagger into the mobile hut with my crates I am greeted by a vision of post-apocalyptic hell. There are drink cans and cigarette stubs in plant pots, clumps of hair and splatters of blood on the floor, bits of chewed food on the desks. I am startled by a noise behind me and turn to see a large rat disappearing through a broken window. Nothing natural could flourish here.

This is confirmed by the arrival of Gareth Gunner, a dangerous boy who is in the same class as his twin brother, the equally frightening but slightly less violent Gavin. Gareth is wandering the room in a daze. “Hi Gareth,“I say nervously. There’s no way he’s coming into my lesson today. “Gareth, we agreed you’d go to the unit. Don’t you remember?” A puzzled expression crosses his face, then he stiffens as the smell of tobacco wafts into the room. It’s Wendy from the referral unit, accompanied by the caretaker, Roy Striper. I’m alarmed to see that Roy is carrying a cattle prodder, although, as he gets closer, I realise it is in fact a device for picking up litter. Gareth goes quietly.

I have 10 minutes to create a stimulating and fluid learning environment. I run through my lesson plan. I’ve managed to squeeze 34 learning strategies into 45 minutes and I’m feeling optimistic as Sandy enters seconds ahead of 8D. I’m about to start when Gavin Gunner bursts in and noisily makes his way to his usual seat in the middle of the third row. He fixes me with a stare.

I try to appear calm. “OK everyone, what did we learn about druids in the last lesson?” A hand shoots up in the front row. It belongs to Jennifer Morrison, the only middle-class child at St Brian’s. I know this because she is wearing an Alice band and her skirt falls below her knicker line. I smile. “Yes, Jennifer?” I can always rely on her for an intelligent answer.

“Miss, we didn’t do anything. Gareth Gunner punched a hole in the door and Mr Striper had to give him an injection.”

I speed things up. We rush through peer marking, key words on the interactive board, a brainstorm, a role-play with me in the lead as a druid mystic. Gavin remains a simmering presence throughout, however, and, sure enough, just as I am preparing the grand finale - a live internet link-up with the education centre at Stonehenge - he jumps on to his desk and dives forward. There is a loud scream as Jennifer Morrison disappears in a scrum of bodies. I watch her Alice band fly across the classroom.

As Roy Striper escorts the last wounded child from the classroom, Sandy approaches my desk. This could be the end. “Hmm,” she begins. “Your interacting variables were shaky, Charity, and your gender equity needs a bit of work, but I think your manipulatives pulled you through. See you in June.”

Next week: Charity is feeling sick - and guilty