Bus operators will often find it economical to convert retired buses to use as permanent training buses for driver training, rather than taking a regular service bus out of use. Some large operators also converted retired buses into tow bus vehicles, to act as tow trucks.
Explain to an 8 year old child that is not yet 49 tall that the safety equipment built into the vehicle is for adults  not children, and a child needs to continue to use the proper equipment (booster seat) so that the adult equipment will fit, and be able to protect, their bodies in the event of a crash.
Usually a child can be moved to a booster when they are too big for a harnessed carseat, and once they are able to sit properly in a seatbelt. A child should be in some type of booster seat until the adult seat belt fits correctly, generally around 8-12 years old and 4'9 tall (Also see Question 9 below).