On Tuesday the unthinkable happened. It came from nowhere. Well, actually it probably came from the drains, but that doesn't sound quite so intriguing.
Nothing could prepare us for the sight of it. Its gnashing fangs. Its grotesquely hairy body. And the size of it. Honestly, it must have been almost as large as a dog. Well, OK, so it was a standard household spider size, but in my own arachnophobic mind, it was like the beast from oblivion.
Life in the classroom has taught me to cope with many things: arguments, nose bleeds, and that panicky feeling you get when you realise this week's lesson resources did not mysteriously materialise over the weekend like you had hoped.
But I have never quite managed to tackle the spider issue. More fool me.
The class had just settled for the afternoon, when it marched boldly across my pathway and over to the book corner.
I shall be eternally grateful to the group of children who screamed louder than me - their angst was a great distraction from the fact that I was edging for the door and hyperventilating.
Some of the bigger boys suggested they could squash it with a broom.
Another one claimed he was handy with an aerosol and a lighter, and would "nuke" it if I gave him 20p.
But salvation came in the form of one of the smallest girls in the class who said she really did not mind picking it up with her hands and taking it outside.
"Just do what you have to do," I whispered nervously, all of my adult credibility rapidly dissolving, as this arachnid savvy child took control.
She released the beast, and thoughtfully warned me that spiders like to go about in pairs.
Needless to say, she has now claimed a new role on the classroom responsibilities rota: expert spider monitor
Louisa Leaman is a London teacher