Without speculating about the driver or the vehicle, thanks to the wonders of streetview, we can look at the scene and even more important, the approach to it.
I understand from the reports that this fatal crash occurred on Lansdowne Lane, Bath.
If the link works, this is where traffic approaching the scene downhill turns off the main road whose speed limit is 50mph.https://maps.google.co.uk/maps?q=Lansdo ... .02,,0,6.1
At that point, there's nothing but the view of the general landscape to alert anybody that they are about to go down a very steep hill. The road is signed as being subject to the national speed limit (60mph on a single carriageway) and there's a width restriction. Apart from futile SLOW markings on the road, using streetview (so I may have missed something) a road user is some way down the hill before they are quite suddenly confronted with a STEEP HILL 20% sign (that's one in five in the old money) and a sign warning of a zig-zag bend.
Further down the hill, there are countdown markers to the start of the 30mph, warnings of speed enforcement and other signs of so-called accident prevention measures.
I would be speculating if I suggested that the vehicle involved in this collision may not have been the only such lorry delivering big loads of building materials along this route, school or no school.
As a society, we allow this type of thing to happen.
I speak as a grandparent who often walks with small children in public. Thankfully there are no really steep hills around here. My thoughts are with the as yet unnamed grandmother of the deceased Mitzie Stready, who is lying in hospital seriously injured. There but for fortune...