Anyone else using my kid to get information to me is inappropriate, in my opinion. Whatever the information or how innocuous it seems.
I believe GuruNet's second definition of inappropriate applies here: Not in keeping with conventional mores; indecorous: improper behavior.
How about this? Little 8-year-old Sally comes home one day and tells you that the bus driver told everyone that she is a Wiccan which is like being a good witch. Being a good witch never hurt anybody, did it mommy?
Would you like that?
Now, all that said, I still think termination is a little steep for the first offense, in this case. But that's only because I agree with your message. I'd want the "good witch" fired.
The founders of the United States of America were mainly comprised of theists. The library of Congress is filled with documents generated as a result of the efforts of our founding fathers and these documents support a specific worldview. Namely, that the God of Abraham, Isaac and Jacob is in charge of the universe, and in particular, of America's formation and destiny. Wicca, Islam, Buddhism, Zoroastrianism, Scientology, various pagan religious manifestations and many more, are all practiced unimpeded in this nation, but none had any impact on, or factored into the thinking of our founding fathers or their writings.
For this bus driver to promote healthy ideas of morality that are in opposition to the current trend toward political correctness may alarm some of the less mature among us, but to those who remember a saner time, her defiance of the devil's minion is rather reassuring.