Negima!? Magister Negi Magi Season 1

Negi Springfield has graduated from magic school and is sent off to Japan to further his studies. He becomes the homeroom/english teacher at an exclusive private school and has run-ins with an enemy of his father, as well as with Asuna, who makes his life a living hell, and that's before she discovers his secret. He learns about (and from) his students and about himself in order to become a master mage, like his father before him.