Archie wasn't stupid - he'd been a student at one time and he knew how exciting it was to sneak out into Hogsmeade and explore, have fun. However, he also knew that he couldn't tell her that. He was supoosed to be a teacher - an authority figure - and to tell one of his students that he had done the same things probably wouldn't be this best idea.
Sitting down across from her, he smiled. "So, Miss Windsor, what are you doing out in Hogsmeade this evening. I'm pretty sure there wasn't a trip this weekend."