Talk about an old work horse. I see these things all the time. Their like a giant block of cheese on wheels. Brings back a great many good memories from my school days.
A North American export. Quite possible, a DOD School system order that was eventually retired from service at its US Military base. US Dept of Transportation has Very high saftey standards for these things. They are very stoutly built. Not at all surprising to see one repurposed and still in use.