AIBU to have rung another school about this?

[Aethelfleda]

I was walking my DCs to their school (let's call it School A) this morning, when the traffic coming along beside us had a lady driving her three DCs to another school (School B). As they passed us (fairly slowly as the road is busy at that time of day) I noticed that none of the three Dc in her car were seatbelted, one in the front and two in the back. It wasn't clear whether they were sat on booster seats (they all looked about 8-10 years) or whether they were siblings or a carshare. They definitely were not wearing belts though. They all had school B's jumpers on.
As I walked the DCs the rest of the way it kept niggling me how much I am annoyed by parents that don't belt their kids in, mostly cos it's not fair on the kids in the event of a crash. Those kids clearly were used to not belting up as they were

I don't get it. What's it got to do with the school? Surely if you're going to ring anyone it would be the police.

yabu - what has it got to do with you?

Please can people comment on the other thread? This one posted before I'd finished. surely, please read the other post where I will hopefuly answer your question.

Yes sorry I don't know what you expect the school to do about it, ring 101 if you want to tell someone

School B won't do anything about it.
I wouldn't do it, but if you must interfere I'd be ringing police with registration number.