Earlier quoted context omitted.
The NHTSA recognizes that large busses are not cars and use a different solution. Large school buses are heavier and distribute crash forces differently than passenger cars and light trucks do. Because of these differences, bus passengers experience much less crash force than those in passenger cars, light trucks, and vans. NHTSA decided the best way to provide crash protection to passengers of large school buses is…
This NTSB PSA video explains it like "eggs in a carton" [0], but those bus seats look like regular benches, zero molding for an actual fit, like an egg would have inside a carton from all sides. I understand that getting a horde of kids to put on seatbelts is a compliance nightmare, but imho it's difficult to argue how that wouldn't make a massive difference in a crash scenario, particularly during roll-over incident…
I can't remember ever seeing pictures of a city bus (as opposed to a long distance bus) overturned in an accident in Europe. City bus-type vehicles are used for public bus service and school bus service ("school bus" is a usage, not a type of vehicle) but searching for things like "bus crash England" shows very, very few cases where a bus has overturned, even when it's come off the road and slid down a slope.
If [1] is anything to go by, the bus needs to hit a similarly heavy vehicle to overturn. Could the American school bus design be susceptible to climbing up/rolling over a car, then tipping, compared to the typical European low-floor lower-centre-of-gravity bus?
(No doubt there are other factors that influence the American school bus design.)
[1] https://www.theguardian.com/uk/2009/dec/16/bus-toppled-colli...