When a pupil sees a teacher outside of school, it’s like seeing a dog walk on its hind legs. At least, that’s how Janis describes it in Mean Girls. So stumbling across a picture on social media of a teacher wearing a sombrero, glassy-eyed and grinning like they are three mojitos down must be like seeing a dog deliver a word-perfect rendition of The Charge of the Light Brigade.

We try not to let this happen, of course. We all know our school social media policies inside out. Right? Right.

But sometimes, for some reason, a pupil still manages to find us. Often, they’ll stumble across our professional profile. Many of us are now on Twitter, either stealthily following accounts or pontificating with the best of them. Many of our profiles are public - and why not? We’re not saying anything dodgy. We’re not posting social pictures of ourselves. We shouldn’t be too worried.

Except…Twitter can sometimes be a nasty little place. And sometimes you tweet something - a picture of a message - without really thinking about how it looks to someone else. Someone who is 14 years old. Someone who has a vested interest in mocking you.

Also, you wouldn’t invite your pupils to a CPD chat in school, so why would you let them in on social media?

Then there is the fact that, actually, your professional account is not just a professional account, is it? What has watching The Fall on Netflix got to do with the optimisation of reading attainment? What has your complaint tweet to the local bus company got to do with trigonometry?

Do yourself a favour: set yourself to private. You don’t need the hassle.

But what if it is not the professional, public account they discover; what if they find “personal” you on Facebook, or TikTok, or Instagram? If that happens, then I’m going to be blunt: you’ve failed.

Yes, children are clever. But they are not as clever as you. Your name should not be your real name. Your profile picture should not be a picture of you. Your privacy should be set to, “Don’t mess with me, I’m the human manifestation of GDPR.”

For many years, I was “Gma” on Facebook. My picture was a Guy Bourdin photograph of a pair of disembodied legs, sitting at a railway station. Far from being confused, many thought it was my best look. I was happy, reader, to accept that compliment.

If you do this thing right, kids shouldn’t be able to find you. But let’s say you do all that and a friend request still pings up from Annie in 10B, what then?

First, decline. Second, report it to the school. Third, reset and calibrate all your privacy settings and change your username.

There are no grey areas here. Students don’t belong in your personal life. Particularly if you have a habit of posting pictures of yourself in a sombrero, grinning madly, three mojitos down. Which is definitely not something I would do.

Gemma Corby is a supply teacher in the north-west of England

This article originally appeared in the 2 October 2020 issue under the headline “When private goes public”