Apparently the bus driver was discussing subjects the parents felt were inappropriate, with the very young students.
If you discuss inappropriate subjects with my children, I think that is undermining my authority, and I will complain - as these parents did.
I think the school board acted appropriately in disciplining the bus driver. Perhaps they went overboard, but they did so in support of a conservative value you claim to support - that of parental authority.
"Perhaps they (school board) went overboard"
Yes.
"...they did so in support of a conservative value you claim to support - that of parental authority"
Nope...don't buy it.