Teachers mispronouncing romanized names of foreign origin - Is there a linguistic explanation?

This is a common stereotype about teachers in (American) schools horribly mispronouncing foreign students' names. I have noticed this a lot, but also in a more general sense. I'm not talking about just using American English sounds instead of those from the original language, but moreso switching around syllables or inserting random syllables that aren't in the word at all. In the most respectful way possible, is there an explanation as to why this happens so often, or why pronouncing unknown words comes more easily to some people than others?