If kids Twitter about their teachers, can they be policed by school boards?

Let me start with an abridged quote from Voltaire:
“I may not agree with what you say, but I will defend your right to say it”.

Students at Brampton’s St. Marguerite d’Youville Secondary, in
Ontario, Canada were tweeting each other about their teachers as reported by http://www.thestar.com/news/gta/article/1291360--brampton-students-suspended-for-twitter-comments-about-teachers on Friday November 23rd.

”...comments were made off school property and on private time, but the forum — Twitter — is public, and that’s enough to warrant a suspension, says the school board.”

One censor was claimed as to have said:
“We strongly believe that the consequences meted out were well in line with the inappropriateness of the commentary,” said Bruce Campbell, spokesman for the Dufferin-Peel Catholic School Board.

Students were suspended from two to seven days.

Further it was reported that : The school’s principal, Kevin Greco, spoke to the school Thursday morning on the subject of “dignity and respect, regardless of the medium,” , however he failed to mention anything about freedom of speech in public.

Are these censors Canadian clowns or what? Isn’t this awful?