I remember hearing once that a actual real group of people who live in Salem call themselves Witches, they don't practice magic though, but are more in line with the old medieval Witches that were similair to Medicine Men before they ended up being accosiated with the devil. The point though is that the group refers to both it's male and female participants as Witches. If one can assume the American Wizarding World follows this practice in how they also refer to males as Witches, then Salem might be co-ed.

 

In case anyone was interested: the school in Ireland I mentioned was a fudged memory of a Pottermore snippet/Chocolate Frog card of Queen Maeve, which said "Legendary witch who trained young sorcerers in Ireland prior to the establishment of Hogwarts School of Witchcraft and Wizardry."

 

I live in England, so Hogwarts.