I can understand the frustration... believe me.
I would add just one more thing to the mix, that the principal and the *person* who can't figure out which way is up might want to be aware of. A US flag flown upside-down is a signal of distress, as in "help us!". In today's world, it being flown in front of a school can bring to mind all sorts of potential problems....
But what to do about it, since the school administration is apparently oblivious?
What about... retraining them? What if some outside group or person were to come in, talk about respect for the flag and what it stands for, and re-establish that old practice of an honor guard to raise the flag each morning, and take it down each afternoon? Some folks might want to have it up all day, but I personally would rather see it treated respectfully twice a day than treated ignobly for the whole day.
You might be able to get a local Veterans group to help with the practice.
Bypass the adults who've forgotten the reason for respect. Go straight to the kids who can still learn it.