People still use the term "co-ed" in the west, since it means co-educational.
However, in the west it's a bit more sexist since it usually only refers to women (ex: the term "hot college co-eds"). The origin of the word actually comes from how only men went to school, and all the females were referred to as co-eds (quite the opposite of all these co-ed mangas). It then became a term where co-ed implied women, when exposed to a male-centric environment, are somehow more willing to put out.
There are a ton of regular and single gender high-schools in the west, but the term "co-ed" has mainly dropped. If you start looking for it, you'll start hearing it more.