The funny thing is that although they look like something out of the 1940's, these are all new. Apparently, the yellow colo(u)r was designated for all school buses in the USA and Canada in 1939, and is officially called National School Bus Glossy Yellow, in case you're looking for it in a paint store.
Although most school buses still don't have seat belts (and boy do those kids travel when the bus is involved in a collision), they are equipped with several safety devices these days. The most important is a STOP sign on a barrier which you can just about see on this photo. Following far too many accidents where children exited the bus, and ran around the front, straight into the path of a car, now when the bus stops, a large red STOP sign on a barrier, wings out into the road to prevent cars from passing. And woe betide any car driver who doesn't stop or who tries to pass the bus.