>cutting student skin doesn't make sense because they can withstand bullets and explosions waah
Why can't you consider the possibility that halos have selective defenses? There wouldn't be any point for medical aid students to have tools like syringes if only super destructive weapons can break their skin. Students can get sick from eating rotten food. They also express pain from minor accidents like tripping. The true nature of halos are not revealed yet but the game has been pretty consistent in showing that they are protected from immediately lethal sources of damage but can still get minor bruises, scrapes or cuts in their everyday life. The "setting" only requires students to be hard to kill while they shoot each other so it makes sense that their halo would only protect them from stuff that quickly kills a normal person