Human mages always left to go to Dalaran until the Third War of course. No mage order or school exists for them in Kul Tiras.You don't have to go to Dalaran specifically to study the arcane. Even if you did, Kul Tiras is a major port city and the Kul Tirans have never been strictly isolated to the region.
Side note: One of the Horde bosses in the Battle for Dazar'alor raid is mage/monk duo. The mage is a male Kul Tiran.