So Holly is learning English with me, and at the local uni (pffft!), and simultaneously on the internet. I realise this when she knows every slang word to every pop song, and when she drops her pencil, and accompanies it with a loud "Fuck!"
I look surreptitiously at the other students, some of whom are all of 13 years old, and realise swearing in a new language just isn't that impressive.
"¿Dónde aprendiste a hablar palabras malas, Holly?" I question, in my terrible terrible spanish, hoping that if any of them did hear or recognise it, that will suffice as The Teacher Disapproving of it.

Next day, and Holly is dropping things again. "¡Mierda!" she mutters, and I reprimand her again. Not that I care, but I already hear rumours that I'm the strictest teacher in the whole Andean mini city, I don't want to get a reputation for being the foulest mouthed, too. "oh, okay," she replies in English, then continues with several tonnes of force to yell "Fuck, fuck, fuck, fuck, FUCK!" as a more polite alternative.

"Holly!" I remonstrate, but there's nothing I can say. Fuck is clearly a punctuation word, just as it was in London, and not offensive. Or a cool word, maybe. And this is the problem when students get to a level approaching fluent, too - that you just can't, for want of a better word, fuck about with English slang, you need to know exactly when it is appropriate and when it's a slap in the face with a wet fish, or you're going to be in very very hot water.

So I sigh, sit across the classroom, prepare a mental speech in Bad Spanish, and launch into a description of how (In Theory) when I worked in London, in colegio, a student who used Holly's favourite word would have certain rapid consequences. (In Theory). Their carrera would terminate. (In Theory) They would end the day by looking for a new school. (In Theory)

It's not exactly true, but it's a context. You want to use that word, you need to know its texture. I think again about the stories of what really did happen in that London colegio, and how tame "Fuck, fuck, fuck, fuck, fuck, FUCK" really was, and cross two fingers behind my back.

Holly's embarrassed. After a minute or two of silence, she mutters to her textbook, in English, "sorry."