I would say that yes, this is an MYOB situation. If you decide to try and corral these kids, you'll be doing it for the rest of the school year and probably for a couple of grade levels.
If you're truly worried that they will hurt themselves, call the parents and let them know of the potential dangers. Otherwise, just deal with them as you would any other kid who was looking for attention (which seems like what these kids are doing). If it was me, I'd probably talk to the kids and ask them why they're running around so much and try to get them to chill a little. I tend to treat kids like small adults -- I talk to them almost like I'm talking to a peer, and it's amazing the effect that has on the wilder kids. They're used to the concept of being able to run wild because they're kids. When I ask them how their day is so far and what kind of a day they think it will be, they tend to stop and think about it. (Either that, or they're silently thinking, "Who IS this lame grown-up?"

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