"Who threw that Buick?" The group's playful chatter suddenly fell into embarrassed silence. "David? Joseph? Come on, admit it." The amplified voice paused a moment, but no response was given. "I'm not laughing here. If I can't turn my back for ten seconds without you chucking stuff into the air, none of you are going to pass."

The students looked back and forth at each other, at their shoes, at their dashboards. No one said anything.

A weary sigh came through the loudspeakers. "Fine, I don't even need to know who did it this time. Just don't let it happen again." Papers rustled, the familiar sound of the evaluation logbook. "Let's try once more before lunch. This time remember you need to grab the cars at the front end, where the engine block is. If you try from the roof your magnet will lose grip, no matter how smooth you are on the controls. Joseph, I'm talking to you."

"Get the cranes back to center. Pull the dozers up. Backhoe two, come a few degrees clockwise. More... a little more... stop. Great. Cue the music, and, five! six! seven! eight!"