I made a girl cry the other day. Proper, sit-outside-for-a-moment, send-for-the-mother tears. This, in many ways, is the pinnacle of my teaching career so far. I feel as if I’ve crossed an invisible barrier. I am no longer desperate to be liked, I just want to get my work in.

Surprisingly enough, I didn’t feel eaten up with guilt. My class waited expectantly. In any normal situation, I’m always the one who buckles first. In Ms Warren’s discipline-free zone, you’re more likely to see me in tears than any member of Year 8.

But mercifully, just for once, my conscience refused to kick in. I didn’t do anything, I let her go. A new, purposeful atmosphere descended on to the class. I smelt something I hadn’t smelt before. Fear. You can’t mess with Miss. My teaching has entered a new era. Anno Discipline.

When I decided to become a teacher, my friends were quick to point out that there were many problems. Apart from lack of pay and your own phone line, two major obstacles stood in my path to pedagogical success. First, I don’t have a very loud voice. Second, I’m too short.

Underlying this is an often unspoken assumption. You need to be aggressive to survive in teaching. You need to be over-bearing and you need to be able to shout. I can do neither. I never buy the drinks when I go out simply because it takes me an hour to get seen at a bar, let alone served. I don’t know if you’ve ever studied the picture that accompanies this column. Look carefully at that head and shoulders. Enjoy them. There isn’t much more of me.

I could tell it was a problem when I was applying for jobs. Heads would look at me with one, dominant thought. This girl simply isn’t scary enough. In the end, we had to change my reference. “Gemma may look quiet and placid, but do not be fooled by this carefully constructed facade. She has the mind-set of a pathological killer. In the right conditions she has been known to become extremely aggressive and violent and has a criminal record consisting of driving over the speed limit and ten counts of GBH.”

Bingo. I got the job.

Kids expect scary teachers. “Be firm, but fair,” the teaching manuals say. I’d disagree with that. Being fair takes too much time. Just be firm. I need to stop all this likeable teacher stuff, spending every morning listening to tragic homework excuses which nearly always end up with having to make a cup of tea which isn’t for me. I need to change my attitude. Love may inspire respect, but hate gets homework. Long meaningful chats with Ms Warren make for no free periods.

So of course I went and found the girl afterwards in the loos. I’d be lying if I said that I could handle being horrible for longer than 40 minutes.

“You know the difference with you, Miss?” she said, sniffing into her cup of tea made with my last sodding tea bag. “You really like us.”

I realised in a flash, that yes, I really do. Damn. The manual doesn’t tell you that this is a fatal obstacle to being a complete bitch.

“I’ll get that homework done for you tonight, Miss,” she said. And do you know something? She did. And it was good.

I think that my discipline tactics are beginning to pay off. Quiet, but deadly.

Gemma Warren teaches atthe Latymer School, Edmonton, north London