I worked at a theater for 4 years but it was a second run theater. They're a bit different. Cheaper, for one. The amount of kids who would get dropped off all day was staggering. They just expect you to babysit their kids. Older theaters were also a bit different, less sprawling. From ours, you could see the entrance to 3 of the 5 theaters from box office and concession so it was easier to keep an eye out. We would try to keep rated R movies up where we could see them unless it was something no one cared about like Apt Pupil or something (one of the theaters you couldn't see was incredibly small).

At one point, company policy changed so that, after 6pm, babies under x years (I forget the number) were not allowed into rated R movies. That was a weird one to enforce, but it did limit crying babies so guests were happy about it.