Professor Wolfe has kindly offered to tutor Mary Lennox in mathematics. And they do, in fact, spend most of the time allotted to the tutoring sessions talking about math. It is a subject in which Mary earnestly wishes to excel, and her scores have improved tremendously.
Just not quite all of the time.
"There is something queer about the dog," Mary says, scowling. "It is the sort of thing that would happen in Milliways - not here. It is not our sort of Magic."