Have you ever heard of freedom of speech?
Freedom of speech should protect kids from gettin expelle from a state institution for a 9 sec clip.
Nonsense.
This isn't a 'free speech' issue, the students remain at liberty to express their racism, ignorance, and hate in any venue they so desire, any time they desire. No government or agent of the government is seeking to preempt the students' racist speech, or silence their racist speech, or subject them to any punitive measures as a consequence of their racist speech.
The students were expelled as a consequence of their conduct, not speech – where their conduct of advocating such criminal acts as lynching contributes to a hostile environment at the school, in violation of the school's policy, where when students seek to foment a hostile environment, expulsion is warranted.