Quite often when I travel down A19 North Yorkshire area (Thirsk, Northallerton) there is a 2 tone blue Mercedes Benz Vario up and down with the schoolkids logo.

It certainly doesn't look DDA compliant and today I managed to get reg it's 
GN05 DZU,  looks like it has 869 displayed as number, but that could be irrelevant 

Who operates this vehicle, and should it not be DDA?