This could be quite a lightning-rod. What if the parents were to file suit against the school and the district. The idea would not be to get damages; it would be to try to create a landmark case to draw attention to this sort of thing and demonstrate what an abject failure the system is in teaching students the essentials of our system of government.
This isn't the first time. If you can stand the shrill voice of a harpy teacher screeching at a student, get this, a recording of the teacher trouncing a student for daring to criticize Obama:
https://www.youtube.com/watch?v=p59MSsLv7Vc
Teacher Tries To Marker Out Honor Student's Romney/Ryan T-shirt: This Is A "Democratic School"