Personally, I think "women only" and "men only" shooting classes are good ideas. It's distracting shooting with a woman who is a beginner. Men seem to naturally want to "help" the beginning woman shooter. The reverse doesn't seem to be true - just human nature, I suppose. If I'm trying to learn new techniques or practice old ones, etc. with a group of guys, it's counter productive being distracted by men paying too much attention to, or "helping" women students. Neither sex is at fault - it's just the way things tend to be.
However, once men and women are well into the shooting sports, I don't think having mixed classes matters as much.