I have a couple of teacher anecdotes. Both of them are from colleagues.
A teacher was working with her class to improve their language as many students were sprinkling their conversations with crude words. She was marking compositions and noticed that one fellow had written, "They were walking in the forest bum had trouble seeing as the trees made it pretty dark in there." She called the student over and asked him to reread his writing to see if he wanted to change anything. He read it and said, "No. It's good." The teacher then read his writing aloud to him to see if he could hear a problem. "No. It's good." She then told him that the word bum didn't make any sense in the sentence. He said, "But I thought it was more polite to say bum than butt."
Another teacher was supervising recess on the playground when some kindergarten students came running to her to report that some grade two kids were saying "swears". When asked what words were the problem, the kindergartens said, "Ooh, they were saying the X-E-X word!"