(I received this question at the start of the school year but it bears repeating.)
Unfortunately, many schools adopt a hands-off policy when it comes to teacher-student assignments, and frown upon parents campaigning and angling for a specific teacher. When the teacher assignment list goes out, it is usually final. You really are at the mercy of the classroom your child gets, or talking to the principal to see if there is any way you could make a change, but only if it’s based on some tangible, specific circumstance or need.
If school hasn’t started yet and you don’t really know what the teacher is like, (ie. your fears are based on rumors or gossip), perhaps take a wait-and-see approach to find out if your child does OK with the teacher. Sometimes the situation will surprise you and your child actually ends up adjusting to and liking the teacher after things settle down into the routine of school life.
If things still don’t feel comfortable, maybe you could volunteer in the classroom to offer support where needed and keep an eye on the situation. If you do happen to hear something disturbing coming from your child or witness an egregious incident, start taking notes and log what is happening with dates and times. Then go with your notes to the principal to discuss a solution. If need be, go to your local district superiors and file a report.
In any case, this might be a first in a long line of potential life lessons you can help guide your child through. We’ve all had to deal with a boss or co-worker who doesn’t communicate well or has a tricky personality. Learning to be adaptable, learning how to get a long, managing differing expectations with different personalities are all life skills worth learning.