Ouritsu Majutsu Gakuin no "Maou" Kyoukan

A group of students enroll at the prestigious magician-training Royal Magic Academy. With faith and ambition in their hearts, what awaited them was Elros, the former sage of the hero's party, feared as a ruthless and unparalleled instructor at the Academy. "Those unsuitable for being a magician will be recommended for expulsion." The students all have their own reasons for wanting to become a magician, though each of them also harbor secrets that could get them expelled. Elros uncovers everything, and the students become cornered. Under such extreme conditions, and through Elros' unorthodox teachings, the students awaken to become true sorcerers! (Source: Overlap, translated)