Here is the truth: I have favourites. I also have the opposite of favourites. I have tried to think of a less clumsy phrase than "not favourites" but I haven't yet come across a word which describes how I feel about this particular group without crossing into nasty territory. It's not that I hate them – I don't – I save all my hatred for pointless bureaucracy and petty staffroom politics. Instead these students, just, well, they're not my favourites.

All my students fall into three categories: favourite, not favourite and "meh". The categorisation of these students is wholly subjective (and often spectacularly random) so admitting to these behaviours in school is frowned upon. I am perfectly happy to confess in private but I'd rather be caught stealing the office manager's handbag than treating students differently depending on their favourite status because that would make me the kind of shoddy teacher that we complain about to our therapists.

Although the categorisation of students can be random, sometimes it takes something miniscule to change a group. Perhaps you will be my favourite because you show me kindness, even just a glimmer of it. You'll smile at me not because you're trying to get an extension on a deadline or you're hoping I won't notice that your hair turned red overnight, but just because. You won't join in when the class decides to play a game of Derail the Lesson. You'll be kind – gloriously, uncomplicatedly kind. And just like that you'll appear on my mental list of favourites.

The granting of the not favourite status is a little more murky. All the reasons I can think of only highlight my immaturity – "she was mean to me and I don't like her" etc. While I indulge this, I am self-aware enough to know that I have not yet left my high school years entirely behind me. There is a pointlessness but assured unavoidability to basing my self-esteem on what a 14-year-old thinks of me – thank you, popular girls in my high school circa 1997, that's all down to you.

How do I manage the favourites and the not favourites? Camouflage. I have a giant birthday chart, like the ones you usually see in pre-schools, in my classroom. Whether I'd give you a kidney or whether I'd quite like to stand on your toe, you are on that birthday chart and you will get exactly the same little card and chocolate on your birthday. I will remind everyone around me that today is your special day and at the end of the day I will ask if you've had a good birthday.

This leads me to the next strategy: FITYMI ("fake it 'til you make it"). It works with and for everything: public speaking, caring about everyone in your class, talking to the head of department about the test you haven't finished setting yet but which you feel "very confident" about.

It is from not favourites that I learn the most about myself as a teacher. There is a final year student in one of my classes who looks at me as though I am trying to nick her mobile. From her I learn the art of not caring about what others think of me. I try to avoid buying into the idea that because you're a student, you're somehow less and so I don't need to care about your opinions. I do need to care, but I need to have limits. From this Queen Bee of the Dark Side, I am learning that those limits need to shift, not just with students, but with people in general.

The most remarkable moment is when a student moves from the not favourite to the favourite list. There is a senior girl who, when she initially met me, loved to engage in a game of Derail the Lesson. Then one day it changed. I hadn't ever responded to her comments or behaviour in the way that she'd expected. I'd used my trusty FITYMI strategy and it didn't let me down. During break or after class, when I would greet her I would smile, genuinely with nascent crows feet and all. She has now decided that I'm not such a baddy and we're working together on building her academic confidence and her wholly understandable fear of showing any vulnerability.

There isn't always a happy ending though. Sometimes, I get nowhere; my FITYMI strategy fails and the camouflage is patchy. Then I just wait the year out. When the student is irritating me or I have to share a space with them I sing ABBA songs in my head and pretend that I am dressed just like Agnetha Fältskog circa 1974. A little unusual perhaps, but a hell of a lot more fun than counting backwards from 10.

This week's Secret Teacher works in a secondary school in South Africa.

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