[OH] How can public schools punish students for what should be basic rights? Zero tolerance question.

My 17 year old daughter and her friends have been having problems with a former friend. I know my daughter isn't 100% innocent but this other girl started the problems and lots of angry texts have been exchanged from both sides. Today this girl decided to attack my daughter. From what my daughter and the school has told me this girl came up and just started punching my daughter. My daughter did not fight back because she does not want to be suspended. She isn't being punished and the school is punishing the girl who attacked her.

According to the school's zero tolerance policy ANYONE caught fighting will be suspended. She is afraid of missing days and falling behind in her classes because she has a full class schedule this year and always has a hard time playing catch up. But what I don't understand is how the school can punish someone for defending themselves? I have asked the school and can't get a straight answer. In the real world if someone would charge you with fists flying you could defend yourself so you could get away. Why isn't that the same at public schools? Luckily, there was a couple teachers across the room and our daughter is fine. But I worry that if the adults hadn't been there would she have gotten really hurt by trying to follow the rules?