Eiyuu Kyoushitsu

A long time ago, there existed a Demon Lord who terrorized throughout the world until a Hero stepped up to the stage and challenged the Demon Lord, ultimately defeating him and ending his reign. The Hero then created Rosewood Academy, an academy made to help heroes-in-training achieve supremacy and help defend the world when needed that enrolls only the best of the best. The story follows the students' struggles in their quest to become heroes.