I don't know if this helps, but when my students say something like, "I'm not going to do this assignment. It sucks." I reply with:
"That is your right, however you had better then be prepared to live with the consequences of your actions."
I am for freedom of expression (For example, when kids ask my opinion on issues I refuse to give it, because I don't want to influence what they believe. When they ask me what to do a persuasive speech on, I say..."What are you passionate about." Much of what I do is to try and get teenagers to find their voice (expression) and be able to back up their beliefs with evidence.), however it must take place within the rules of the school, the rights of others, and respect for peers and teachers in the room.