If the agent wishes to move the perfect updater in the direction of what it perceives as the truth then its best tactic is probably just to share all of its information with the perfect updater. Only if it wishes to move the perfect updater's beliefs away from its own should it selectively withhold information.

Not so. The agent in question has an information advantage over another, including information about what the intended pupil believes about aspiring teacher. It knows exactly how the pupil will react to stimulus. The task then is to feed whichever combination of information leads to the state closest to that of the teacher. This is probably not sharing all information. It is probably sharing nearly all information with a some perfectly selected differences or omissions here and there.

Dan's point still stands even in this idealised case.