A Piece of My Heart is 5 female leads. any extras can be used as soldiers. It's set in Vietnam. You may have to remove a few dirty words if it's for a Catholic school, though.
From my experience some females like the opportunity to play a male role. You should inquire with the students first. Some of the online reviews I have read indicate that females love the opportunity to play a male role. do you guys ever peek at angies list?