It's not pretty.
Update: Well, dang. The video appears to be gone. (It might be somewhere else on YouTube, but I haven't time at the moment to look for it. There are plenty of similar pranks anyway.)
It was a pretty funny series of scenes of teachers dancing behind students who were being interviewed on video, said students being unaware that anything was going on in the background. The teachers are mostly good dancers, and a lot of them are hilarious. But the link is now defunct. So I repeat, dang. (Pardon my strong language.)by