I don't let the "I hate you"s slide. I tell DD6 that they hurt my feelings and she apologizes and I notice that she makes more effort not to say it when she gets toward tantrum stage.
I also don't let other bad behaviors slide. I know she does behave much better in the class but she learns her social behaviors first within the family. I know a child that kicked and hit her mother when she didn't like something and she was BFF with DD when in preschool. As they got to be good friends, this child would then kick or hit DD when DD said she wanted to play with someone else. And then Dd tried to kick me at home. Luckily we just ended the relationship and reinforced that she cannot kick without severe consequences.
I just wrote a letter to the teachers, cc principal. A boy in DD's class is bullying her. First incident she told me about and I just said to ignore (though my mother bear instincts actually wrote a letter to the teachers -- but stopped myself from sending as premature). On a field trip two weeks ago, I saw the boy deliberately push himself through where DD was standing, getting ready to hear the farm lady. DD reacted verbally and I hushed her. Later I told her to ignore the boy because her yelling at him was what he wanted. This boy is more than a head taller than DD, so pushing is a force for her. I saw in the school yard, before school, Dd was talking to a friend, who was about 6 inches away. This boy walked between them, pushing his way through. DD ignored. It seems the more she ignores, the more he does this. She told me that yesterday he swung his lunch bag and hit her 3 times, without saying sorry. She told the assistant teacher but it crossed the line for me and I wrote the teachers and principal. I let her know that no one can hit her like this or push her. She has to know what is acceptable at school, at home. It is the same.
I think they have to learn very early good behavior starts at home.
Ren
