Oshioki: Gakuen Reijou Kousei Keikaku
Genres: Hentai
Type: OVA, Episodes: 3
Aired: Nov 18, 2011 to Jun 15, 2012
Studio: Studio 9 Maiami
Source: Visual novel
Rating: Rx - Hentai
Synopsis:
My name is Shimohei Joutarou. There is a reason that I'm here, at my new place of work, despite the fact that the school year hasn't started.

On that first day, I almost immediately came across Mitsuki's and Minami's secret. I then heard about Mahiru, younger sister of Classics teacher Kuji Hinako, and the astonishing improvement of her grades. I then discover indications of Hinako's backdoor maneuverings.

Now, it is up to me to rehabilitate these students who break the rules.

(Source: translated and adapted from official site by Cranston)