As soon as you tell someone, it won't belong to you anymore. And it will be out of your hands.

But now that you're thinking it, it's already out of your hands. Or will be, whenever you next run into Lady Lestrange.

She'd likely appreciate your pro-activeness.

But this is where occlusion would be useful, wouldn't it?

And yeah, 'course I'll help you. Though I've never taught anyone before, keep in mind.

There are probably ways to make the lessons interesting, though.