It's not meant to be interpreted like a computer program, it's meant to be interpreted like law. I'm pretty confident that a judge could reasonably conclude there's an implied "any" quantifier for children, with 1 child satisfying the criteria. Regardless, here's some caselaw that said it only means when children are arriving and leaving:

https://scholar.google.com/scholar_case?case=173803621968999...

Indeed, here in Michigan most of these signs have hours that they apply, sometimes it's like 7:00 am-4:00pm, other times they split it into a morning and afternoon session...

In my pre-law days, I tried to argue to an Illinois county judge that it meant outside not just kids were inside the school that day. Got the ticket anyway.

Wow, the judge considered kids to be present when there were no kids around? That seems pretty outrageous, if the sign said "present".

That doesn't seem to comport with how people actually drive when students are in school but not visible. It also seems questionable to require people to know whether kids are in a school at any given time. You can be fairly sure they're there Mon-Fri during most non-summer weeks of the year, but there are also kids at the school after school for many hours, practicing sports/drama/science bowl.

I'm pretty sure I'd get honked at if I drove 25 MPH past a school in a 35 MPH zone at 5p on a weekday, if there were no kids around.

I think the judge just got it wrong, and maybe have just been pissed a 19 year old was fighting a ticket in his court.

Seems like an absurd reading of that language to me.