My gut reaction is that if other kids are reporting it to the point that the daycare worker takes it seriously rather than brushing it off as "just kids" then there is a serious problem with the driver.
The driver's behavior is obviously disturbing the other kids enough that they are trying to get help.
Does the driver work for the school or a bus company that contracts with the school? I think you need to make a complaint about the issue, especially since the driver has "history".
Long term, we need school choice. But so long as the leftis want to run things, fine. It's their mess. And we have to find a way to get America's kids educated. So...
"The driver's behavior is obviously disturbing the other kids enough that they are trying to get help."
Ditto that. And it could be a PR nightmare for the local school system. You have the upper hand.
I had a cousin who was suspended for sneezing too much on a bus. Yes, sneezing. I called the local paper. The school system decided not to suspend my cousin. Never made print in the paper. Would have been a hoot.
I wasn't in a position to negotiate on behalf of my cousin. You are for your son. And if things don't go the way you want them, you can inflict serious pain on them.