I would have told her to prove that pot was deadly, to prove that you were wrong, and I would have refused to leave the room being that she had no grounds to kick you out. But that's being that I'm incredibly stubborn.
Now, you weren't entirely right to go off on that tangent. You should have just done the assignment by talking about the supposed bad things about pot - the myths, the truth. Like someone already said, you could have talked about what she said were the bad effects and state why you think otherwise.
Or, you could have wrote down why you disagreed with the assignment itself. I've done that before.
However, she still had no right to kick you out. Not doing an assignment right is not grounds for disciplinary action, unless you broke up the sentences by writing HEIL HITLER in between. The very most she should have done is made you rewrite the paper.
We could be missing a part of the story. If you were disrespectful in your paper, like you started raving about how stupid she was for teaching you this or something along those lines, then she would be more in the right. And that is possible; we all have a tendency to retell stories in our favor. Additionally, we also don't know the manor you took when she started opposing you. If you got really mad and started sniping at her, then that also means her acts were justified.
But assuming that's not the case, take it up with your principal. Ask him/her what she thinks and try to tell the story as honestly as you can because you know that the principal is going to go talk to the teacher.
Remember, however, to keep cool, dignified, and respectful. No one's going to listen to some kid who's whining and bitching about being yelled at. They will, on the other hand, listen to someone who lays out a logical argument in a calm and collected fashion. They expect you to be pissy; they expect you to yell and be very angry about it because that's what a lot of kids would do. Don't do that; it will dig your grave even further.
Keep in mind, also, that when you're talking to your principal and working out the problem, you're the subordinate in that situation. Your principal is probably more likely to first take sides with your teacher partially because of the status that you have and partially just because of the fact that your story seems almost ridiculous. So, make sure you're solid when you talk to them. Make sure you don't sound immature, like you're just mad because someone insulted pot. Think it out and don't get mad.
