Not long ago I taught my kids the concept of the golden rule. I was getting tired of their complaining and arguing about what one had done to the other, not sharing, being rude, kicking, etc. Unfortunately my oldest, who normally has a very kind heart took those words and to my surprise twisted them around to say that if her sister did something mean to her she was allowed to do the same back to her. Absolutely not. Then she actually told me that it was true because her teacher had said so in class. I have spent the past couple of weeks fighting her on this. Admittedly I was not in the classroom when the teacher said it, but I'm sure my daughter misinterpreted her words. As much as I tried to explain this to my daughter the more she insisted that she was right. Darn stubborn gene - not sure where she gets that from. Finally I reminded her of what I used to say before she would go to a friend's house unsupervised - the rules that her father and I set for them, trump the rules of anyone else. Teacher, friend's parent, babysitter, whoever. So even if she truly believes that her teacher said that if someone is mean to you, you can be mean back, be the better kid and either ignore what the other kid is doing (if it's just a little annoying), or talk about the problem if someone hurt her feelings or hurt her physically. I think she has finally accepted that concept, which given her usual adherence to rules means she will probably follow it.
I have to say this whole thing hurt me because it showed that my smart and normally very sweet girl was being mean on purpose and thought she was justified in doing so.