"It's only cheating if you get caught..."

In October, I was grading a set of tests when I noticed two students had the exact same answer. Nothing too special about that, except the answer was wrong. Nothing too out of the ordinary about that either, except that the exact same error each student made was remarkably obscure.
My "teacher radar" (as my colleagues later called it) was up and running, and so the next day after class, I called up the two students in question for a little chat.
"OK guys, I'm going to ask you something. And your honesty in this matter will carry a lot of weight." (pause for effect) "Did you guys cheat on the test?"
Both of them: "No."
"Well, here's why I ask," I said, whipping out the tests. "That's pretty strange that the two of you made this same, rather obscure, error. So are you sure?"
The girl: "No."
The guy: "No." (pause) "Wellll....sometimes my eyes wander."
In my own head: "WTF does that mean?"
"So what, exactly, does that mean?" (nice job, inner censor)
Then he goes on some long excuseplanation about how he's under a lot of pressure from his folks to do well, and sob-story-this and sob-story-that. He eventually gets around to asking what the consequences are.
I said, "Well, I really don't know. There are many ways this can play out. The worst outcome for you would be that I'll call home, report this to the principal, and it'll go on your official record. Which will entail you, the principal, myself and your parents all sitting down and discussing this." At this point, he nearly peed on the floor. "So right now, I don't know. I'll have to think about it."
He's a good kid, and I certainly recognized the value in having him live with fear in order to keep him on the straight-and-narrow from that point on.
After letting him sweat it out for a day, I told him that I was going to give him an F on the test, and I made sure he recognized just how generous I was being. He knows I'm all over him now, as I've given him good stare-downs during the tests since. So that's worked out well.

Before that instance, I was under the impression that the students doing poorly, or those in lower-level classes, would be more likely to copy off another student. But that's not the case at all. The lower-level kids tend to either not give a rat's ass about their grade, so cheating is most certainly not worth the effort, or they have a lot more pride in their work - "I studied hard. I want to earn this. My work is my work." It's the upper-level kids, the honors kids, who tend to cheat more. They, as the eye-wanderer exemplified, are often under a lot of pressure - both from their folks and self-inflicted - to do well. Of course there is no always-true rule, but generally speaking, that's what I've found to be true.