I still would advise my kids to not gripe on a public forum about any of their teachers. Nor I would be let them join any "I hate Joe Schmoe" group, you know the Facebook groups that kids set up when they decide to pick on a peer?
But kids who do engage in such activities online are perhaps rejoicing after hearing that a federal magistrate ruled that a student who created a Facebook page to complain about her teacher was protected under the 1st amendment. Apparently in 2007, a senior named Katie Evans said this about her teacher "the worst teacher I've ever met". She took down the page a few days, got suspended by the school's principal, and got moved from her advanced placement classes to regular classes. The principal got sued and the magistrate ruled that the suspension was unconstitutional AND asked the principal to compensate the student who was "wrongly" suspended.
I think there's something wrong with this whole thought process. Let's see how it plays out in future cases.