When my kids were young I reminded them to take the time to buckle their seat belt when they sat down. While my local bus has seat belts, it's not federally mandated for full buses and many buses to do not have seat belts. Only New Jersey and New York require seat belts on newly purchased full size buses. Kids today are so drilled to wear them that my daughter was very flustered that the bus would take off even before she finished managing to buckle herself. One day her seat did not have a seat buckle and she was hysterical! It might be a good idea to talk with your child about this.
You might also want to remind your child to gather all their belongings before they get off the bus. I read a great tip on parenting.com They suggested you tell your child you won't be mad if they leave something on the bus, or if their school work blows out onto the street. The last thing you want to do is see your child race into the street to chase something, or try to run toward the bus as it's pulling away. You might want to read the parenting.com article for more tips: http://www.parenting.com/article/school-bus-safety-21354686
By the way, PennDOT reminds motorists that if you see a bus with its red lights flashing and stop arm extended, you must stop at least 10 feet from the bus. You're required to stop whether you're driving towards the bus, or behind it. PennDOT says drivers who encounter a school bus stopping on the opposite side of a divided highway are not required to stop. Don't forget to slow down to the posted speed of 15mph in school zones. Violators will face hefty fines and points on their driving record.