When I met my daughter's teacher I told her off.
How did you go about telling the teacher off?
By saying that she must concentrate on teaching her students not playing favorites.
You should show your daughter's teacher respect, it is important to respect authority figures. If you disrespect your daughter's teacher it will make things very awkward for your daughter.
I'm showing her that if you do bad you should get punished.
You will be the one who gets punished, because you shouldn't really talk down to a teacher like that. She has all of the power over your daughter and isn't someone that you should want to make enemies with.