It was a responsibility that fell to her. She wasn't happy about that, but that didn't mean that she didn't make the best job of it that she could.
Discipline was a very serious matter. It wasn't just about making sure that a girl was properly punished for her misbehaviour, it was also about the deterrent effect.
Of course, a damned good hiding acted as a deterrent for the girl punished. But it also provided a deterrent for her fellows too - they heard the strokes and the cries, saw the tears and, often, the girl's marked bottom as well.
That's why she liked to deal with naughty girls in the bathroom, door locked. Turning the key and putting it into a pocket made the point that what was to follow was inescapable.
And, the hard, reflective surfaces seemed to magnify the sounds. Making it impossible for anyone anywhere else in the building to be unaware that a disobedient girl was getting her just desserts...