I often wondered that myself. I have a class B license to drive buses in CA, and I have noticed that the shorter buses have them (those short ones that the special kids arrive in school in), but the larger buses do not have belts.

I always assumed that if the bus ever got into an accident with a minivan, that it really wouldn't be a big deal for the occupants in the bus. It would take a crash with another bus or a semi-truck to really cause alot of damage.

I think Brent is correct also, in that the safety record of buses tends to be much lower than your typical driver. But I would like to see school buses install belts. It would teach the kids good safety habits and keep them in their seats in the event of an accident. The cage/frame in the bus will protect the kids from any major harm, but I am sure they will get thrown around inside enough to break some limbs and crack some heads.

I have a friend who was driving a school bus and someone ran a red light and t-boned the bus. The kids in the bus didn't even know they got hit. It felt like a small bump in the road. The driver stopped and checked for damage. The bus lost some paint on the side, and the car that hit it (Nissan Pulsar, I think) was totalled. The bus escaped with just some dents and some scrapes.