I came to realize this when the head of the school our son went to called me at home to say that my son had used an inappropriate word in school. He wouldn't say what the word was, even when prompted several times, as though he was unable to utter it. Then finally he resorted to spelling out 'f u c k', so I said 'Oh, you mean 'fuck'' and he nearly lost it. I explained to him that my son learned pretty much all of his slang from his schoolmates since he'd only been in the country less than a year so probably the problem was on his end and left it at that. He never did call again...