Suspect it was originally a rural school bus. Used to be heaps of these in the bush picking up kids from outlaying farms and running them into the local rural primary school. Usually seated 15-20 and spent most of their time on dirt roads away from the larger towns. My Nephews attended a primary school like this in the 1980's, only had 12 students from Kindergarten to year 6 with 1 teacher who lived in a house located at the school. Sadly it closed many years ago, but there used to be hundreds of these little schools all over the country and was often the first posting many teachers got. How far "Outback" do I hear you ask. Well it was a little town called Windeyer in NSW between Mudgee and Bathurst about 260 km (160 Miles) 3.5 hours drive from Sydney. Back then it had about 500 metres of tar road, a pub/store, a church, half a dozen houses, the local manual telephone exchange and the school. Now very popular with the 4WD crowd, good camping and good gold prospecting.
Cheers Stephen