I’ve realised that there are two kinds of people in this world. There are those who dump their empty crisp packets on your desk, and there are those who cut out their Free Books For Schools tokens and put them in the handily marked container. Oh, and there’s a third kind of person. There’s the person who’s stupid enough to volunteer to cut them all out in the first place. Just call me empty crisp packet co-ordinator. I feel honoured to be asked.

This, and many other similarly philosophical thoughts occur to me in those odd moments when I’m sitting in school, doing something that doesn’t seem even remotely connected with teaching. Watch out for my new book, Philosophical Reflections of a Teacher Who Cuts out Crisp Packets. Recently, this - how can we put it - “diversification” is happening more and more.

There’s one thing you’ve got to get clear when you enter teaching. Accountants do figures. PR consultants make phone calls. Lawyers and barristers argue complex cases in court. Teachers do not teach.

They dress up in funny outfits, they decorate classrooms, they police the playground ensuring that Year 7s don’t throw themselves under cars at the end of the day, and that Year 13 stick to heavy petting and don’t indulge in full blown sex in view of the collected parents. Teachers spend three hours after school trying to construct the Free Books For Schools collecting bin, which comes in a flat pack and was obviously designed by someone who does not understand the time pressures of being a teacher. Or an English teacher who has trouble working sanitary towels with wings, let alone a cardboard monstrosity with a gynaecological array of flaps and orifices. Being a teacher is like being a Rubik’s Cube. You have many sides. You’re a state-sponsored schizophrenic.

Last Monday found me with my Year 12s, trying to have a serious discussion about the city as a symbol in modernist literature. Try as I might, they kept on laughing. In the end, I stopped my earnest exposition. “What’s the matter?”

I snapped. “We just can’t take you seriously, Miss.” I caught sight of myself in the reflection of my window. Of course, I was dressed up like a St Trinian’s girl with my hair in bunches, and my brother’s old school blazer.

Did I forget to mention that? Just another run-of-the-mill thing you’re supposed to do on a non-uniform day. “For this you got a first-class degree,”

sniffed my mum the night before as she was carefully ripping holes in my new pair of Marks and Sparks opaque black tights.

Red Nose Day saw me up on a stage with other venerable members of my profession doing a carefully choreographed dance routine to “California Dreaming”. Obviously. The Christmas bazaar saw me trying to smash as many meringues as I could with a baseball bat on a floor covered in jelly, as you do on the Friday before Christ was born. And guess who had to clear up the jelly afterwards? I’m like an actress: which role would you like today? Lady Macbeth or My Little Pony?

And now I’m sitting in the staffroom, cutting up hundreds of mouldy old crisp packets. And they say teaching isn’t glamourous. Maybe I could add scissors wielding skills to my CV. “Do you know how many germs are contained in those bags?” said a helpful member of the chemistry department.

We’ve all got the mug that everyone buys us for birthdays and Christmas. I have several, and I’ve even got the poster. “Cat-watcher, Administrator, Pen Pusher, Shit-Shoveller, Sex-Slave... TEACHER!” it happily pronounces, or something like that anyway. I’ve heard of life imitating art. But life imitating a mug? Hold that philosophical thought, I want to get off.

So when does the Kate Moss role kick in?

Gemma Warren teaches at The Latymer School, Edmonton, north London .