Undesirable fire alarms

 In my school we have had a problem for a few weeks : one student keeps activating the fire alarms

We mustn't activate the fire alarm without a good reason because the students have to leave their class and go under the rain and they become sad.
The fire alarm is used to warn  if there is a fire in the school. Then the students don't panic because they know the fire alarm is a fake. If there is a real fire, they don't move too fast even if the school is on fire.