When I was in 6th grade my class went on a one week school trip to a camp in upstate New York called Frost Valley. On the very first day, practically as soon as we got there, a couple of guys started talking about doing the California Knockout. One guy stood up against the wall and invited his friend to administer the chest compression necessary to induce said knockout. I remember at the time thinking it was one of the stupidest and clearly dangerous things I had seen my classmates do.
You can't keep a good bad idea down, though, and know the dread California Knockout has surfaced in Korea under the infinitely less interesting name "The Choking Game". Gusts of Popular feeling has a great post on the issue with pictures that look exactly as I remember. This time around, however, there seems to be a solo version played with a noose that looks like some sort of kiddie version of autoerotic asphyxiation.
Not to oversimplify things, but I believe that the cure to this kind of boredom-induced tomfoolery is probably sports. Let these kids play some sports, Korea! Something that lets them work the arms, perhaps, because soccer obviously is not doing it for them.