First, it is very sad that your child is unhappy. Children should enjoy school and their childhood.

You should first go and talk to the teacher, not the principal.

This will give you a chance to at least hear his/ her side of the situation.

If the problem is not resolved then tell him/her that you will take your concerns to the principal.

It is not wise at this early stage to form some kind of parents union. You represent this as a problem your child is having - keep it at that level until you have spoken to the teacher and the principal first.