It seems to me that some of this issue and how to approach it really depends upon the specific child and his/her attitude toward authority.
Some kids are naturally resistant to authority. These are kids who might get in trouble somewhat regularly or are the "lawyers" who question every bit of every rule ever handed down to them looking for loopholes. When a teacher is wrong with this kid, it might be a good time for him learn some lessons about respecting authority and managing his tone to elicit good reactions from his audience.
But for other kids, those who start from a position of respect for authority and who pride themselves on following the rules, the experience of having a teacher who is wrong might be a good opportunity for them to learn to *challenge* authority. Blind obedience is, IMHO, just as bad for a kid as blind disobedience. I think our goal should be to try to get kids from both ends of the spectrum to the middle, where they understand appropriate times and methods for challenging authority.
For our part, DS9's 1st grade teacher was not a good one, but DS9 was a rule-follower. I was actually relieved when he (mostly politely, given that he was a 6yo) challenged the teacher a few times because it told me that he was not a sheep, that he would stand up for himself if the situation called for it, that if things were bad he would let us all know it. We talked a lot about the situation and that we could disagree with what the teacher did, but that we should still be respectful and polite. That there's a right way and a wrong way to approach the situation.
3 years later, he is still very respectful of authority, but he is also a kid who respects himself enough to speak up politely if something is wrong. I am very proud of this aspect of his personality. I think he has a real strength of character.
Just another point of view...
