It is possible that the bus has been cut down, but you would have to wonder why would anyone have gone to the trouble.
Short buses were called "activity buses" in North Carolina (at least) and were used to take small groups of students to off-campus activities. The ones I have seen were about the size of the van-based "Head Start" school buses now used, except they had a conventional 1-ton truck chassis with dual rear wheels.
My guess is that it is an original "activity bus".
