Insane bug: if you allow your students to get dumb enough, they start dealing negative damage, which simply put heals the enemy. This would not be an issue with the normal dragon fight, but becomes one with the school duel, where if you happen to click fight it stops you from exiting, and with both students healing each other only, it softlocks you and the only way to get out of it is to load a save or restart.
Didn't know this, had to reload a save that was 2 hours back.