If students lose all their HP and their teammates can’t protect them, they’ll “fall in battle.” When this happens, they receive a random "sentence," or consequence, that they must fulfill. (Sentences are listed in the Book of Laments so that you can check them off the list once students complete them.)
Their teammates will also take damage. By default, each team member will lose 10 HP (you can change this in your class settings). If another student’s HP is already low when this damage happens, this will create a cascade effect where they fall in battle, too — resulting in another team-wide loss of HP.
That said, the same student can’t fall twice as a result of the original incident. To keep everyone safe, teams should be proactive about using their powers to keep each other’s HP and AP high.
The behavioral benefits
Obviously, this can get out of hand quickly if students don't help each other! For this reason, there's a strong motivator among students to help each other so they can avoid getting to the point where they fall in battle and lose a lot of HP.
Your students will start to do some "self-policing." If they're acting out in class, their teammates will say things like, "Hey, calm down. We don't want to lose points today!" Or they might say, "You've been tardy every single day this week, and it's starting to hurt our team. You've got to come to class on time."
As a result, there's a shift from the teacher policing the class to students doing it themselves. Therefore, students will take ownership of their behavior much more readily.