Arya snuck in behind the Head Girl, literally. She was taller and easier to hide behind than one of the younger students. But the idea wasn't so great when the girl decided to volunteer for stuff, making the short man aware of their presence, though she was sure he'd spotted them long before. Maybe now was a good time to offer up an answer for dueling rules...

Doing a bit of strolling to put some distance between herself and the she-snake, she unholstered her wand, twirling it idly. "No physical constant between duelist."