Hm... sorry. That was actually meant to be a playful ribbing of "If you're just here to see your kid, please leave, you're disrupting the class". The way she said "[u]Headmaster[/u] Death" is more than welcome to stay is to mean that, because he's the headmaster, of course he could stay.

tl;dr, it was her very convoluted and playful way of saying "if you're just here to visit your son then please leave". It was by no means an order. I'm sorry if it sounded like one ;w; 

Also, I looked over my post and there were no grammar mistakes. A few convoluted uses of passive voice, maybe, but other than that I ran my post over with a spellcheck just to be sure and I still got nothing.