"Taking a stick and beating an effigy of a presidential candidate is a politically charged act," True, but the kids didn't beat an effigy of one candidate, they beat both of them thereby expressing contempt for politicians in general and not one side of the political spectrum.

Contempt for politicians in general places them well within the mainstream of US culture and to suggest that this act is outside the "legal limits" of the students' freedom of speech is a bit of a head scratcher.