If it's getting violent, don't fight back. Using scissors against someone is using a weapon, and if someone gets hurt, they could be in really big trouble, and not just at school, but with law enforcement. DO NOT FIGHT BACK. You could get in just as much trouble, even though it's technically self-defense.
Tell your drama teacher, or whoever's coordinating the play. She (or he) can help you, and might take the instigators out of the play.