Why do thirty or so well-dressed women line up outside a Greek house?

So I’m driving home last night, and I’m travelling down a block…. well, actually I was parked across the street (long story) from what I believe to be a fraternity, although it could be a sorority, too. There are about five such “fraternities” on the block. Outside each one is a line of thirty or so women, all dressed to the nines in high heels, fancy dresses and fur coats. I hear a female voice yelling, “All right girls, get ready.” I sit there for a moment, and then it looks like one or two women enter the building.

As I drive down the street, I see similar lines outside the other buildings with greek letters on them. Now, if the greeks are sororities, then I suppose this could be a rush (at this time of year?) However, if they are fraternities, and I don’t hear any signs of partying (usually you can hear the music from blocks away, and there’s a keg or two sitting on the porch, and lots of casually dressed (or semi-dressed) men consuming said beverage.

Can anyone explain this?