what about ALOT of confetti in air conditioner (those who don’t have central) and putting it on money saver… everyone should be far away from a/c… and also instead of recording conversation make a special recording with everybody screaming for five seconds and then 5 minutes of quiet till 5th time where teacher is waiting for it to happen so everyone screams for a minute(harder to find the recorder).
Shut off the main breaker for all lights on that floor and when everyone comes out to check spray them with fire extinguisher.