[quote=dreamingflowers]Katherine knows who he is, and quite possibly what he's doing in his spare team. It wouldn't be completely ridiculous if she "dreamed" about him.[/quote]

He's not a secret. Those students relevant to him are supposed to be in the know, and I like to think he has periodic meetings with each of them (which he would take about as seriously as the students) in order to double-check they're not going to go whacko and sabotage another family. He also won't bother to keep his extracurricular activities secret - it's not in his interest for emerging (in more ways than one) members of the magical community to be ignorant of what he does.