If the school isn't using the seatbelt bus he wont be catching it. Sydney drivers are just too careless.
I guess it's all a matter of perception lol. DH and I have been spending a lot of time out near the hawkesbury and Blue Mountains lately and TBH we find the country drivers a whole heap more scary. They go at crazy speeds on narrow bendy back roads and seem to lack the awareness of other cars/traffic sense of Sydney drivers.
I would guess that neither demographic is better at driving - they just have different styles that suit their local conditions.
That said of all the accidents I've seen in Australia the country ones seem worse - probably because they're more often high speed crashes rather than bingles in slow traffic.

my children spend 2hr on a bus to and from school - half of which is spent travelling on the busy newell highway with semi trailers and B-Doubles wizzing past at 100km an hour
That sounds like my childhood school bus ride (probably the same for half of Australia's rural population lol). I have such fond memories of those rides - they were so social because we didn't just ride with the kids from our school but also the high school kids (the big kids lol - they seemed so grown up) and the special school kids and the kids that went to the private school. Even if I wasn't feeling social I loved watching out the window (still do - old habits die hard) or having time with my book.