So, we're not entirely sure what's going on here, but the person who originally uploaded this video to Facebook claims that it happened in a Kentucky hotel on Wednesday, and was done to mark the start of the Olympics.
Here's her full description:
So, I'm in Kentucky for work and today when we got back, 1000 high school students had checked into our hotel. They had been making quite the ruckus tonight, but then did this to celebrate the start of the Olympics. Not the best video, (cause my fear kept me pretty far from the edge) but that's 18 levels of them singing! Amazing!
As far as flash mobs go, this one is pretty damn good.