Freak out? They'd just been practising to defend themselves, so nobody was going to freak out, right?
Hmm. Kiri found that when she applied that hypothesis to reality, it didn't hold up. The unearthly screech echoing through the classroom made her grip her wand as tightly as she could.

There was a second possibility, and it was much more worrying. Everyone had their wands drawn, everyone was at least moderately fuelled by adrenaline at this point, and it sounded as if merpeople were preparing an ambush outside the door. The implications weren't nice. Nervous students with their wands pointing at each other... Someone could get hurt. Kiri waited anxiously for Professor Lawson to return.