My students sometimes say, "You're one of those freedom teachers." I don't mind noise in the room as long as it's productive, and if a kid needs to stand while he writes his story, so be it! If someone made me sit in a desk for 6-hours, I'd be crazy.
I try to have fun, and I think the most productive class periods are the ones when I don't have to talk much at all. The kids know what to do, and they're busy doing it!
I do have rules and guidelines, of course, and I really make sure to teach procedures/protocols--which is something elementary teachers are great at, but sometimes middle school teachers lose.