See Me After Class (2012) Anime Watch

The story revolves around Yuuki Kagami, a boy who enrolls in the academy of his dreams as a honors student — and is mistakenly put in the girls' dormitory where boys are prohibited. Faced with the possibility of having to leave the school, Yuuki has to dress up as a girl in the dormitory. On top of things, he ends up rooming with the female teacher Ayana Kakinozaka, who has to watch over him.