Look at the picture - go on, look. Three months ago I was a fresh-faced young thing, new to the PGCE course. I had a gleam in my eye, pockets full of peace and love and a Glastonbury tan to die for. Now look at me. I’m a wreck.

Tragic isn’t it? Only 15 weeks in and already I’m tired about the eyes and my hair has lost its shine. My back is bent, my throat is sore and my feet hurt. I’ve got frown lines a foot deep. I’m exhausted but I can’t sleep. And whose fault is it? Bloody Year 9, that’s who!

Something strange is going on in 9:1. I can’t work it out. Is it the material, the range of activities, the time of day? Am I too hard on them, or too easy? Did I do something bad in a former life and am I now having to pay by spending five periods a week being persecuted by a bunch of14-year-olds?

There has to be a key, some mystical technique to get them to pay attention for more than 10 seconds. What can it be, that magical ingredient that turns a bunch of moody adolescents into a finely-tuned, creative team who’ll sail through the national tests?

It’s not like I want an award or anything. Right now I’d be happy if they’d just stop chewing gum, answering their mobile phones and discussing who snogs best out of the boys in their year.

The typical lessons start, despite all my Kyriacou-esque preparation, height advantage and now near-perfect killing stare, with me calling for quiet while fielding a torrent of questions and comments about my clothe, private life, and taste in music. The conversation then turns to where Amy got her lippy, who has nicked whose boyfriend and can Lisa have her CD back that she lent to Teresa weeks ago? Oh, and Wayne has punched Sanjeet for sitting in his chair. But I didn’t see it, so I’ve no chance of dispensing justice.

I flip. I shout and say rude things. They argue and answer back. I get louder and say even ruder things. I’m trying to separate the behaviour from the child, but the handbook goes out of the window. I’ve lost. They’ve won. I’ve succumbed to the Dark Side.

Suddenly, it goes quiet. They are all looking at the floor. I’m so stunned I don’t quite know what to say. I begin my lesson. The bell goes for the end of the period. They rise, smile sweetly and stand quietly behind their chairs. Later in the corridor, they are full of cheery “Hello Sirs”, like nothing has happened. It’s scary. It’s Hannibal Lecter country.

And late at night, just when I think I’m safe, they come chattering into my brain, keeping me from sleep as I try to plan the next day’s strategy.

My friends tell me I’ve got it easy. Most of my classes are doing fine, producing good work and even making me laugh. I would happily adopt my entire Year 7 tutor group were it not for the fact that each of them seems to grow several inches taller in his or her sleep each night and I know they would eat me out of house and home. But Year 9 is beyond me. They are a mystery.

Jon Croose is studying for a PGCE at Bristol University