Bus driver's responsibilities?

I was always anxious about sending my son to school on the big bus.  Kids are mean, there are so many children and only one adult, and he's so young.  I was fortunate last year to have a driver that (although I found her mean) took care of the children she had.  I never had a concern about his safety.

The first day of school this year, our driver dropped off the children at our stop and almost drove away with a kindergartener from our stop still on the bus.  The child was not in the first few rows, either.  I attributed this to first day problems, and really wasn't too concerned-it takes time for the children and the drivers to learn the routines.

Moving to day 2...I received a panicked text message from a friend saying her son was not on the bus when it got to his stop (our children are on the same bus, just different stops).  After a child on the bus told her that he got off at a different stop, she drove around the neighborhood and found him at the end of a driveway a few blocks away.  The kind family of strangers who he was let off near kept an eye on him, because there was not a single familiar adult there to receive him, and permission was not given from either of his parents to allow him to exit the bus in a different location.  He's 6 years old and in first grade.  She was waiting for him at his assigned stop.  She was told that because her child is not in kindergarten, he can be let off the bus.

I read a news article from a friend in Mississippi about a child that had fallen asleep on the way to school and was left on a bus all day.  I'm really curious when the drivers should be held accountable (at least in part) for the children in their care.  They chose to be a school bus driver, not a city bus driver.

On the second day of school, I feel the driver should be looking out for the children, especially for the younger children on their bus.  As the year goes on everyone is a bit more comfortable.  This gave me quite a wake-up call.  What is the bus driver's responsibility to our children?  Why isn't care being taken to make sure a small child gets off the bus to an adult?  Should our children wear tags with their stops on their backpacks?  Does your child know what to do if you're not waiting for them, and do they know which bus stop they should be getting off at?

I don't want to frighten any parents, but she was lucky the family that watched him were decent.  We don't like to think that there are bad people in our neighborhoods, but in the 10 minutes he was in unauthorized care, so much could have went wrong.