1年A組のモンスター 1_nen_a_gumi_no_monster
1-nen A-gumi no Monster, a manga by Hideki.

A Private Girls' High is a special school nurturing young maidens to be graceful, delicate intellectuals. However Class 1-A, infamously known as the "Class of Monsters," is full of bullies, blackmailers, scheming sadists, and other trouble makers. Within a week, every teacher who has taught this class has either quit, resigned, or even been imprisoned. The plain-looking Jimi Tarou shall carve out his name and become a legendary teacher.
1-nen a-gumi no monster