To assume Professor Wolfe is unaware of the movements of his class even while is back is turned is, perhaps, foolish.

It would be quite foolish to assume the same of any teacher worth his or her salt, but in this case it is particularly unwise.

Fortunately for the girls, thus far the only sign of awareness on his part is the slight arch of his eyebrow (aimed at the chalkboard) and a slight increase in the volume of his voice as he turns.

And then, of course--

"Miss Merryweather. The verb conjugations, if you would."