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.
Then, they can move to a booster seat. Ages 4 to 8: Children must remain in a booster seat in the back seat of a vehicle until they are at least 8 years old or 57 inches tall. Once they reach that age or height, they can use the regular adult seat belts.