This is sorta awkward, but I think you got mixed up. That sounds just like a script I wrote about two years ago, it's been floating around the net for a while. Slay told me when I showed her that nobody was going to buy the script, but if it's an urban legend now, maybe I ought to give it another shot? I'll bet nobody will believe I wrote it now, though. Dang.
Okay, so anyways, there's this school where all of the students go missing around the middle of the school year, and it happens at the same time every year, to all of the students, only, the teachers and all the staff do too. So there's nobody to spread the news that it's dangerous, right? So anyways... the board of directors send new teachers and staff, and parents send new kids, but then it happens again the same time in the middle of the next semester. And it just keeps going on and on, cause like, nobody's there to report it. And all of the parents just think their kids are jerks who are spending time with their girlfriends or whatever... so then they go there and don't find them... and like... they think, "Dang, where are my kids?" And then they disappear too. So there's nobody to report any of it. The story ends with the disappearances keeping on going on and on... except it's heavily implied that you the viewer, will disappear as well, by scrolling text at the end of the film.
Kind of makes you think, huh?
-Gordon Van Hearst
P.S. Let's try not to talk about this rumor any more so that nobody steals my script.