>>...funny prank<<<
Defamation and slander are not funny. You would not be laughing if you were depicted in the same light as the school principal, or would you?
It really depends. As long as it were taken down when requested then what is the big deal? He deserved a few days of in school suspension but the school was within its rights to punish him how it saw fit but I still think it is just a kid who was doing a stupid kid thing. It is not like he had his principle added to a fake child molester registry or something serious like that. (Such things are not difficult to do.) If the kid were really being malicious and had a history of it then I would agree with the punishment. I suppose when inflation of character becomes a crime then I would be more willing to worry about defamation of such.
It sounds like what this kid did is not substantially different from what we on FR do all the time to Ted Kennedy, Hillery Clinton, etc