Kodomo Gakkyuu

Contrary to her youthful appearance, Umeko Kojima is not a child but instead an unmarried, 22-year-old who also happens to be class 5-2's new homeroom teacher at Ageo Daini Elementary school. Due to Umeko's absurd educational policy coupled with her jaw-dropping super-human strength, her class devolved into an unrelenting hell of bloodshed and conflict. Within that hell, a sworn enemy to Umeko would emerge and a whirlwind of laughter and over-the-top violence would ensue.

[Translated from Noripedia.jp]