Read the volumes of "The Schools of Arcane Magic" found in Dalaran listed below.

Introduction: Spawns in the Teleportation Crystal room, on the floor.
Divination: Spawns in Violet Citadel, near the port to Caverns of Time.
Necromancy: Spawns on top floor of Ledgermain Lodge, in a room with an empty bookshelf.
Conjuration: Spawns in the Violet Citadel, on the bottom floor bookshelf right of Rhonin.
Abjuration: Spawns in the Dalaran Visitor Center, next to the chair and bookshelves.
Transmutation: Spawns on the bottom floor of Ledgermain Lodge, in the empty bookshelf.
Enchantment: Spawns on the second story balcony of the store Threads of Fate.
Illusion: Spawns on a box next to the normal dungeon daily quest giver by Violet Hold.

You can find some great screenshots over on wowhead. Along with a great guide to help