In texas I tried to take a class b non cdl test in a bus that was currently registered as a school bus and they would not let me test, as was said before it needs to be the same class or cdl type,
just to reiterate,
the class of a vehicle is all about the weight, specifically the gvwr listed on the vin plate.
the cdl issue is about what you do with the vehicle according to how it is titled,
and both these vary state by state
my bus thread, http://www.skoolie.net/forums/showthread.php?t=8860&highlight=bubb