I would like to propose teaching the kid about gazilions ways to be cheated. It is ethical, helpful, and (if you insist in the following need) the kid will be equipped with an ability to use the experience to cheat someone. Teaching the kid to cheat without revealing the cheating nature of school is the evilest from the society's PoV.
Interesting take. Though, at the end of the day, it feels a bit like teaching to cheat.