Our car line seems pretty efficient. Parents line up in their cats in front of the gym, circling around to the street. Parents do not get out of their cars, but have a big sign in the windshield that lists the teacher and the child's class number, like TeacherA 3, TeacherB 19, etc. (The kids all know their numbers because they're used in school as well.) A staff members comes around and radios someone inside, calling out the names in order. The kids are in the gym, seated by class, and they are called six at a time, or six families if there are siblings. Then they line up on the sidewalk behind a painted line. Only when a teacher has determined that all cars have stopped moving, the kids are to get in the vehicles. They must enter on the right side. Children are not allowed to walk in front of or between cars. When they load up and pull out, the line moves forward.

In the mornings for drop-off, it's essentially the same. Parents do not leave the vehicles and the students only exit on the right.

I don't know how long the school has been doing it this way, but the line moves pretty quickly.