I REALLY would not leave your son alone, at the bus stop.
No matter what age he is.
It takes only a few seconds, for a child to disappear or get abducted.
Bus stops... are commonly observed by child predators and they know the habits/schedules of buses etc. and could easily see, what house your son walks from, to the bus stop.
Could you... speak to another parent who's child ALSO rides the bus... and perhaps, drop your son off at her house... to then car-pool with her/her kids to the bus stop???? Before you or your Husband goes to work. ON the way to your work, you or Husband can drop your son off at that other Mom's home, to car-pool.
Or, yes, sign up your child for before-care and after-care at the school.
Many schools, have this.
So then you'd just drive your son to school yourself... and drop him off at school, and for before-care at the school. It is supervised.
It does not matter, how 'mature' or 'smart' a child is. Predators don't care about that.
In my State, a TWELVE year old girl, was walking home after school. So of course it was in broad daylight and very busy and lots of people around. As she walked, after awhile, she noticed that a man in a truck was following her. He notice she noticed, and he began to go faster trying to of course, get her. She had the idea to run back to the school. Once she neared there, only then did the man stop and turn around.
This was in a nice upper middle class neighborhood, in a good area, and this was a normal nice girl.
I would NOT, leave my kid alone at a bus stop.