Kusatta Kyoushi no Houteishiki
English name: Bad Teacher Equation
Genres: Boys Love, Comedy, Romance
Type: OVA, Episodes: 2
Aired: Nov 25, 1994 to Nov 24, 1995
Studio: J.C.Staff
Source: Manga
Rating: PG-13 - Teens 13 or older
Synopsis:
Atsushi Arisawa enrolls at Jougaouka High School to be near Masami Shibata (Ma-chan) who was his childhood crush. Unbeknownst to Atsushi, however, Masami no longer works at the school and his brother, Masayoshi is now the nurse. Atsushi mistakes Masayoshi for Masami and is horrified because to him, it appears that Masami's personality has done a complete 180. Add to the fact that Atsushi's friend, Kouji Inagaki is totally in love and constantly trying to make-out with him, Atsushi's life at Jougaoka is hell..until he starts thinking that maybe the new Ma-chan isn't so bad afterall and that, maybe he actually likes the way Ma-chan is now. Until of course, he finds out that Masayoshi isn't Masami. 

(Source: ANN)