I’ve seen this exact graphic in several countries. The boy is older, maybe 12-13, is wearing shorts and seems to be carrying a briefcase. The girl is younger, maybe 9-10, has a pony tail with a very large scrunchie-like thing, seems to be wearing a very short skirt and has a purse. They are running because they are excited about getting to school, or maybe about finally getting out of school and going home. Of course, the real reason they are running is to warn drivers that they might just run right in front of your car. A big mix of assumptions and stereotypes. And despise all this deconstruction, a pretty effective warning sign.
Though the speed limit is still 30mph, which is pretty fast for a school zone, at least by American standards (I suspect also European standards).
I see that graphic so much I would like to know who designed and what they were thinking when they did it.