So a bus is just a free for all then because you don't need a child seat? What's the reasoning behind that, just because of the sheer size and the weight of the bus cushioning the children from harm?
More or less, yeah. Also the height - most of the impact ends up getting absorbed by the bus's undercarriage, and relatively little of it is transferred to the occupants.
Supposedly un-belted bus occupants are safer than belted car occupants, and may even be safer than belted bus occupants, because seat belts tend to cause spinal injuries. Which is why very few school districts opt to install seat belts in their buses.
School buses: also consider the weaponization of the seatbelt by the student to annoy their seat mate; the ramifications of extricating dozens of children should the bus ever end up in a position where seatbelts are designed to prevent release...
