Well, you have my sympathy for taking on a thankless job and trying very sincerely to make the world a better place. For what it's worth, thank you.
Frankly, I think it's the nature of the job: You're going to be in contact with
everyone at some point, and to many of those parents (such as the ones you describe) you're going to be the first person ever to tell them that they are a lousy parent and need to shape up. Regardless of how nicely it is phrased, this is not a pleasant experience for them, and their first (perhaps only) reaction will be defensiveness and outrage--justified or not.
In that sense, it's not unlike being the doctor trying to tell patients that they need to eat their veggies, stop smoking, exercise more: Most folks are going to yell, "Eh, those dumb doctors don't know anything!" and go back to devouring their sugar-frosted deep-fried pigskins, rather than running out to buy a gym membership. It's a human nature, type of thing.
Plus, there's selection bias working against you: Most people remember the really awful teachers they had, but they can't recall the mediocre ones and it's difficult to be good enough to be memorable for that. I remember very clearly the day my high school Algebra teacher told the class that girls shouldn't be taking advanced math and should be in Home Ec instead (yeah, I'm that old, and the guy is long since dead), but the only thing I recall about my fourth grade teacher is that she let us watch NASA launches on TV in class. I can only recall one really great teacher prior to college, and she taught foreign languages, but I'm sure that others must have existed nevertheless.
Sorry I cannot be more helpful. I work for Big Pharma, so I've sort of gotten used to being hated and reviled for my occupation.
