Regarding the arcane spell schools, they are inconsistent kinds of categories, and less useful for organizing spells. No other gaming mechanics should depend on them. Anything that depends on the schools will likewise become an inconsistent mess.
Consider the schools Abjuration, Transmutation, and Necromancy. One category is a purpose, an other is a process, and an other is a theme. Any spell could show up in any category. The schools organize spell lists less well than other organizational systems, such as psionic disciplines and divine domais that are both mainly thematic and can be used to organize all spells coherently by theme.