We have had a few bus crashes/accidents latly in our area. Its scary. I know its said to be safer but I still feel my kids are safer in thier properly used car seats than on a bus. I only let my oldest ride for feild trips and its cause Ive got no other choice. Its ride the bus or dont go. The whole ride I follow the bus and my pulse is elevated for sure.
http://www-fars.nhtsa.dot.gov/
In 2009, 2 school bus passengers and 3 school bus drivers died in school bus accidents. 91 people in other vehicles, 1 person on a bicycle, and 21 pedestrians died in school bus related accidents. Riding behind that bus you are likely in much more danger than your child.
Compare that to 33,808 people killed, total, in automobile accidents that year. 1,538 of those people were children, many riding in vehicles to and from school.
Your children are VERY safe in your automobile, safer than most. But, even properly restrained, in the newest/safest car, with the safest driver- it's hard to imagine they would reach the same level of safety provided by a school bus.