Ah, high school.
My school did homecoming king/queen, chosen from the senior class, and junior-sophomore-freshman prince/princesses, all voted on by the corresponding class (and everyone voted for king/queen). Prom king and queen were nominated/voted on by the senior class.
The town I grew up in is close to a very large Native American reservation, thusly has a large native population. My senior year, the homecoming king was from that group. It got really ugly and some of the "popular" kids were quite vocal and nasty about how it was "reverse racism" because "everyone from X tribe only voted for X because they are from the same tribe, and the 'white vote' was split." Really ridiculous, you would think it was an election for something that actually mattered.
During prom, a nice pair of kids that were well-liked but not part of the popular crowd wound up on the ballot. Everyone voted for them - or at least, enough people did that they won. Again, the cool kids were furious that a pair of "orch dorks" won "their" contest. I found their rage at this pretty hysterical (I was a band nerd, so felt a bit of triumph!)
Contests like this are, in my opinion, exactly what GreenEyedHawk stated they are. And I think they do more damage than good.