People usually react with horror when they find out I teach in a secondary school. I’m small, and they automatically see me working with little ones.

Gemma text = I often think their preconceptions are more a reflection of how they view teenagers than how they view me. Because, let’s face it, teenagers get a pretty bad press. I know someone who lives near an inner-London secondary and is often frightened to walk home when school ends. It’s something about those large gangs of kids crowded ominously in knots, laughing raucously, that gets to her. Perhaps she thinks they’re laughing at her. Welcome to my world, I tell her. She especially doesn’t like big groups charging down the road looking like (and usually believing) they have sole right to the Queen’s highway. I tell her teenagers are a bit like tarantulas. They can be pretty frightening if you try to engage them, but if you ignore them, they’ll ignore you back. Correct me if I’m wrong, animal lovers.

I love working with teenagers. There’s something about their disarming honesty, their capacity for humour and sarcasm, their ferocious intensity, their desire to please and be liked, that warms my heart. Obviously, I’ve had run-ins; it’s not all happy-clappy moments. I’m sure there are students wandering around my school who think I’ve done them wrong. I hope one day they’ll reconsider. I’m sure they’ll realise that conflict can often be the defining experience of secondary school years, whether it’s with teachers, family, friends, or, more often than not, yourself. My tactic is to combine courtesy, humour, and as much love as I can. I know it sounds cheesy, but it’s the only way.

So, I’m on the Tube the other day, struggling with an overnight suitcase.

I’m standing in a carriage, and at the next station a group of six teenage boys get on. They’ve got this way of eating up every spare inch of space, and their loud voices are disconcerting in the hush of the train. Everyone seems to move to the other end of the carriage. I don’t mind where I stand.

I’m not lugging my suitcase one inch further. There’s a jolt and my suitcase goes hurtling into one of the boys and leaves a tiny mark on his trainer. The carriage collectively draws its breath. “You’ve marked my trainers,” he yells at me. Everyone looks down into their papers, the way they do when they sense a confrontation. Nothing like a bit of community spirit. I’m thinking, come on, some of you must have teenagers of your own.

But I know that marking trainers is a cardinal sin when it comes to the teenage years. Strangely enough, when I was younger, your trainers needed to be as dirty as possible. Now, my form put so much effort into keeping their trainers clean they don’t have time to do their homework - so they tell me. “I’m sorry,” I say to the enraged youth in front of me. “It’s crowded. The train jolted. I didn’t mean to mark your trainers, and I’m sorry if I’ve hurt your foot.” The carriage does a double take. The boy looks disconcerted. “That’s a long explanation,” he tells me. “I’m just trying to be polite,” I answer. He discusses this with his friends for a while. They’re trying to work out if I’ve dissed them, but they’re looking for malice that’s not there. They get off at the next station. One of the boys brushes against me. He smiles. “Sorry,” he says, and goes on his way.

Gemma Warren is head of inclusion in a London secondary school. Email: gemmablaker@hotmail.com