Mages are not themselves of any magic school, though they are trained in one or more of them.
The priestess, for instance, has the Creature type High Elf, with the subtype of Westlock. So she would be affected by spells that influence "High Elves", "Elves" or "Westlock". (Although note there are no such spells currently in the game.) She does not have the "Holy" type and thus is not affected by spells that influence Holy creatures.
