pronounciation difficulties

The Japanese alphabet doesn't have the letter "L" so when they encounter it in English words, they simply change it to an "R". So, most of my students actually call me Che-ru-she. If I try to work on it and ask them to identify "la" vs "ra", they insist that I'm saying the same thing and can't hear the difference.
Similarly, the Japanese alphabet is structured so that consonants are almost always followed by a vowel. They come in clusters. This is why they insert the "u" in the middle of my name. They can't say the "r" sound by itself. Sometimes, they seem to drop the vowel at the end of the word, but they have difficultly if it comes in the middle. This is particularly bad with the "s" sound at the beginning of a word, where they always substitute "shi".
We were told never to correct our Japanese co-teachers in class. So even if they say something that is incorrect, we're supposed to let it go because they are our superiors and hierarchy is incredibly important in Japan. So you cringe and bear it. But just before I left school last week, I actually had a teacher tell the class to "clap your hands and sit down." Based on what I've just explained, you can probably figure out why I had trouble stifling a laugh. Luckily, that teacher has a very good sense of humor, so when I explained it to her after class she thought it was funny, too.