Where I grew up in a small town in West Texas you waved to other drivers, because you probably knew them. If they weren't local you knew that also but still generally waved, I'm not sure why but that was the custom. In Dallas, of course not. Jogging or walking here in Alpharetta GA some do, mostly if they've seen you often I think. Jogging with someone in Austin, everyone acknowledged each other regardless. It all depends on where you are and what the customs are, and doesn't mean anything beyond that.
Maybe OP is trying to emphasize the local culture with the school kids, maybe he's out of place, maybe something else; obviously I can't know. But my feeling is that it's safest and most harmonious to adhere to whatever customs prevail in a given area.