Aside from pure logistics of getting/keeping all kids buckled, I think the major points being brought up are that:
1. The seat belts themselves may be more of a safety hazard, especially in the event of a fire or rollover accident.
2. They are very expensive to install/retrofit on buses.
3. The maintenance due to knuckle-headed kids destroying them would be tremendous.
4. The seat belts may lead to additional injuries by said knuckle-headed kids using them as weapons in various manners.
According to the study that someone mentioned earlier, of all of the fatalities across the nation (800), only 5% occurred on a school bus. That is only 40. Not that I don't think that every life is precious -- I do. However, asking me to pay millions more dollars in taxes to fund seatbelts on buses where the risk is very, very small of fatality for the 8/10 of a child that is likely to be killed in the state of Maryland this year, is just not worth it at this point. Yes, I know. Everyone wants to say, but if even one child is saved it's worth it, but there is evidence on the other side that even more children may be injured if seat belts are used. If you want to stick with that argument than all of the parents who think they are protecting their kids by driving their kids to school are actually making them less safe, according to the study mentioned, as 25% of the fatalities were caused in cars with their parents.
People have said that California has instituted seatbelts. All I have to say to that is that Maryland is getting bad enough right now, please don't start running us like California!