*the letter has a standard privacy ward on it which prevents any mention of lycanthropy from being noticed if one of the children's dorm mates should catch sight of the letter.*Dear children,
Use caution when interacting with Professor Lupin and his pack. If they seek you out, be polite and excuse yourselves as quickly as is appropriate. Do not seek them out in turn, and use discretion when speaking to them. I know you already avoid Professor Lupin as much as is practicable.
Continue to do so.Edgar