In my experience, it definitely is a "no-no" to request a certain teacher. I doubt they even write down the request and they publicly state that they cannot promise anything.
I think, like some others posted, that expressing what styles of teaching or types of personalities work well with your child is a good way to open that door. Ask for a teacher who is interested in children who are gifted or who they think will embrace the challenge, etc.
In our schools, although I do not think this is publicized, they do make the class lists at the end of the school year, or very beginning of the summer, so now is the time to talk about it, even if you have very little influence.
ETA: I will also echo that in talking to parents I have always found parents who rave about a certain teacher and other parents who really hated the same teacher. Sorting this out seems like an impossible task. I often would rather leave it to chance, kwim?
Last edited by howdy; 05/01/14 10:35 AM.