What do Iran, Cuba, and the US public school systems have in common? All three persecute online dissidents.
Students are not the property of the schools they attend. They are not inmates in an asylum nor convicts in a prison. The school employees had no cause nor right to punish this student; she did nothing wrong.
This case has absolutely nothing to do with impolite language, and everything to do with a student's willingness to criticize the state employees in charge of her school. If only we had more like her.
School administrators should not be held immune to the criticisms of the students under their care. Educators have a job to do, and that is education. Their students are their customers. Educators are not prison guards, the principal is not a prison warden. The students in their charge are guilty of no crime sufficient to hold them in contempt nor deny them their natural rights. Prison convicts are deserving of punishment when they dispute the policies set down by the warden. The same is not true of students in a public school.
Sadly I don't think that this case is going to result in anything but an increase in the powers of school employees to attack and persecute students whose speech they disagree with. Luckily the students are not without recourse. It has long been said that on the internet no one knows you're a dog. The same thing is true of students, some of whom will simply begin writing online under pseudonyms...just like they do in Iran and Cuba.