What would it take for you to go over the Art teacher's head to the equivalent of the AD? if the Art Teacher didn't think that little Johnny had enough talent to paint with oil as frequently as the other students and only got to paint on days they painted with acrylics? where is the parental outrage meter on that? probably the only time you go to the Principal to complain about the Art Teacher is when a nude model shows up for the kids to draw. otherwise, nobody is going to bat an eye. but parents second guess and question the Coach all the time.
I do agree that, generally speaking, teachers are more receptive to speaking with parents than coaches. largely because those same parents are not going over the teacher's head all the time to complain to the Principal. when your boss gets bad reports about your performance you tend to not love the folks (parents) who keep turning in that sort of news to your boss. when parents second guess your decisions all the time, it's just hard to smile and welcome parents discussions over and over again about the same points (playing time).
best advice for anyone- think twice before you open your mouth about anything. consider the consequences of your actions before doing something you will later regret. you will save yourself a LOT of grief that way and cooler minds will prevail in the end over emotional responses in the heat of the moment. works as baseball parents and sometimes not too bad with the spouse.