We just had our second parent-teacher conference with our almost-four year old's preschool teacher (he's in a Montessori school, that follows the technique well, mostly), and among other things, learned that the main issue the teacher felt that needed to be addressed was his respect for authority - and by that, she clearly meant "doing what he's told".
Both my wife and I believe in raising independent, self-sufficient children who have the emotional and intellectual tools to be successful. We don't believe in a discipline model that relies on parental authority, but in helping our children understand why they need to do what they need to do (whether it's going to bed on time, brushing teeth, not hitting, whatever). We believe that, other than in issues of safety or health, as much as possible they need to find out for themselves why they should or should not do things - with some guidance and suggestions, but ultimately fewer and fewer as they get older.
This clashes with the general discipline model, though; certainly teachers expect that if they tell a student something, he does it, no questions or "talking back", and to a large extent that's seen as necessary. Even in a Montessori classroom, that's still the expectation, and not one we can really do a lot about (other than choose a different school, I suppose).
We understand that, and also understand that in life you ultimately do need to learn when to respect authority - at least apparently: to act respectfully, at least. Whether or not you think the police officer pulling you over is targeting you because of your left-leaning bumper sticker, you still say "Yes, Officer, thank you". We definitely want him to have this experience (hence, not changing classes for this particular reason at least) for this reason - this won't be the only person in authority who expects him to respect her, and the earlier he learns, the better.
As such, what can we do to help our son here? He's not yet four years old, so it's unclear to me how well he can understand the difference between acting respectfully and respecting someone (in the sense of giving more weight to their opinions or requests based on your past relationship with them, for example). He's not a compliant child to begin with; his younger brother clearly is far more compliant, and will likely have much less trouble with this, but our three year old is already his own very independent person and very much likes to keep it that way.
What we don't want to do is simply tell him "You have to listen to your teacher"; that doesn't give him why, for one thing, and relies on his respect for us and/or parental authority that we prefer not to rely on unless absolutely necessary. A good answer will help us give him the tools to deal with someone in authority without expecting him to become a compliant sheep, and the reasons to understand why it might be necessary or appropriate.
Edit: I talked with my wife about what the teacher referred to, and the specific behavior was "not complying quickly with requests", not talking back or challenging authority explicitly. IE, she will tell him, ", go over and do your bead work next", and he'll require several repetitions to actually go do it. This isn't all that different from getting dressed in the morning - except in how we handle it: we let him know what he's going to have time to do if he gets dressed now vs. if he takes until right before we leave to get dressed, and he typically chooses to dress quickly once he's awake enough to think coherently.