Juuninin no Onna Kyoushi
English title: Dirty by the Dozen
Japanese title: 十二人の女教師
Alternative titles: 12 Female Teachers, Juuninin no Jukyoushi, Juuninin no Jokyoushi
Type: OVA
Source: Visual novel
Episodes: 2
Status: Finished Airing
Aired: Apr 11, 2008 to Jul 11, 2008
Duration: 29 min per ep
Rating: Rx - Hentai
Studios: Y.O.U.C
Producers: Digital Works
Licensors: Kitty Media
Genres: Hentai

A horny headmaster and his naughty nephews are out to train twelve teachers to be sex slaves. They'll use any scheme in their arsenal to get the hot lady professors to share their carnal knowledge. But even if the women give their bodies over freely, that doesn't mean they'll just take it lying down. The extracurricular activities are nonstop in every nook and cranny of this institute of lustful learning. 

(Source: AniDB)