Schools have to have set policys the cover all political speech, and then that is questionable because students are allowed to express their political ideas verbally. Limiting the legitimate expression of beliefs is legally harder then not allowing swear words or nudity.
Hey, I don't think it should be that way, but it usually is. High school students have extremely limited rights in the classroom. Schools can assert that anything that causes "classroom disruption" or "distraction from learning" as disallowed, and that is usually simply a matter of somebody's individual discretion. Same as kids don't usually have privacy rights over their personal belongings at school.
I think the kid should have the right to wear a political t-shirt at school. I was surprised that the school allowed that, and seeing that it was dress-down day is telling. Political shirts are probably against the dress code normally.
There are a couple of things that I don't buy about the story. I don't buy the thing where the girl is playing this like everything that happened was an out-of-left-field surprise. If she was wearing the shirt as a political statement, which she should have the right to do (but as a high school student, often DOESN'T have the legal right to do at school), then she would get more mileage saying "I knew people would read my shirt and have different opinions, but the teacher's unprofessional bullying surprised me." Rather than, I don't know what a freaking Republican is.
One reason she would have to lie about her political understanding is that it's possible that her case against the teacher hinges on her not intending to violate the dress code by having no intention to make a political statement. If the teacher saw a political t-shirt, said the girl had to change because it was against the dress down day rules to wear political shirts, and then the girl refused to comply, and THEN the teacher went into the "jokes" and took her into the hall, it's a slightly different story where the girl was directly challenging the teacher's authority and the high school's rules as being unconstitutional. The "I think she did it because she's against Romney" fits this story, because that means there actually was another reason for the teacher to ask her to change.
(I think the rules ARE unconstitutional, but the courts have upheld those rules over and over again because they don't give a shit about 16 year-old political consciousness.)
If she genuinely didn't understand the context of her shirt, her family, and politics in general, I feel terrible for her. It's possible to grow up in a Rush and Hannity household and believe that everyone else you know is just like you. If she is incredibly sheltered (seems likely) and has only ever seen one worldview, maybe she pulled that t-shirt out of her closet and wore it because it was comfortable. Maybe her parents were like "honey you should wear that shirt, it shows you have intelligence and integrity." And she went into school, and the teacher yelled at her and told nasty "jokes" that the girl COULDN'T get because she thought all good people, not just Republicans, were for the Romney-Ryan ticket, and her worldview was completely attacked by the idea that there are racists who support Romney.
I've been in that position, although in weaker circumstances, so I feel for her a lot if that's what's going on here and she really is just being batted around by the adults in this story.