I think the post by HypocriteHunter is well said.  There is too much being read into all of this especially by the authorities.  You are dealing with high-school students, I will presume minors, using a recent technology around which we are still trying to establish rules.  Should any of them have posted something like this?  No (and they didn't).  Is "liking" it a bad decision?  Yes, even if it is your right to speak freely.  Is the correct response to throw the book at them?  NO!!!  The school has a teachable moment regarding racism (or its appearance) and how to behave on a new media that provides the illusion of privacy.  Instead of teaching, let's make use of the maximum consequences available and fear as our lesson, no doubt "pour encourager less autres".  Not all that different than expelling a child for bringing a knife to school to cut a birthday cake for having a weapon.  Poor behavior, poor response - will any good come of this?