Walking into my form room - a biology lab - is always done with a degree of trepidation, but seeing Jacob's body consumed from waist to neck under a 4ft purple snake almost brought on a cardiac arrest. It took me a couple seconds to realise it was a cuddly snake and that neither Jacob's life, nor the snake's, was at risk.
The snake turned out to have been "found" in the playground. The kids called it Skippy. Odd. I always thought that was the name of a kangaroo. I confiscated it on the grounds that, as Jacob was wearing the snake, it was a breach of school uniform.
Animal hazards are becoming an almost weekly occurrence in the labs. I'm now immune to the slowly defrosting dead rats in the sink. And the locusts are a source of endless fascination. We watch every morning as they struggle out of their skins and start to demolish branches. They've changed colour and, when not eating, seem to spend all their time mating.
"What are they doing?" asks Tom curiously. Fortunately, one of the other boys answers for me: "Havin' sex."
"Is that it, then?" asks Tom.
"Is that what?"
"Well, yeah, obviously."
Tom shrugs, nonplussed. "Looks borin' to me. I'm off to maths."
There are other, non-animal hazards. I twitch nervously every time one of the pupils shakes hands with the human skeleton in case the whole thing collapses. My anxiety is well-founded: I walked in one lunchtime to find Jack standing with his palms firmly planted on the torso's breasts. His curiosity had resulted in the womb and foetus falling out, which he thought no one would notice - despite the fact that he had put them back the wrong way up.
Then there are the frankly random classroom objects. Orange flashing road lamps, for example.
"It's mine, Miss, honest."
I point out that it has the London Borough of Ealing stamped on it.
"But I found it, Miss, this morning."
"Outside my house by a hole in the road." Scenes of traffic chaos flash through my mind. I confiscate the lamp and put it next to Skippy.
Off to the ICT suite. Surely nothing hazardous in here? The room is empty except for computers. I feel briefly safe.
Year 9 are writing about what they would do if they were King, Queen or Prime Minister for the day. They have already written, "Ban stupid writing tasks like this one."
Suddenly Myles starts coughing... then he is gasping. He stands up and leans forward, his face red, his eyes bulging. I tell Andrew to run for Nurse. Time seems suspended as I climb over computers and swivel chairs to get to Myles, who is by now making the most hideous noise.
Lirim, seated next to him, thumps Myles hard on the back. I shout at him to do it again, harder. Still Myles flails. Then Lirim does the unbelievable. He grabs Myles around the middle and tries the Heimlich manoeuvre. Myles coughs up saliva and a black pen top.
I look at Lirim. The class is silent. "How did you know how to do that?"
"Seen it on EastEnders, Miss."
Guneet puts his hand up. "Miss, if I was Prime Minister for the day, I'd make every pupil learn first aid."
Julie Greenhough, Teacher of English at a London independent school.