I agree 100 percent. I beleive I wrote this on the other thread- you can agree to disagree. As long as you don’t ilegitimize the school. Meaning saying they are wrong, bad etc.
For the most part though, you should agree with the majoirty of things…
Your father could of added “I beleive you are right, the Rebbi probably made a mistake, or he thought you were talking about something else, or there really are two Avimelech’s” etc.
I don’t think you should ever say “he was wrong” and that’s it. Unless it’s something really horrible, like getting thrown out and publicly shamed for something very small- then you should speak to the principal…and your kid.
I’m saying, always try to add things, be dan lkaf zchut, and show how this is gray and can be interpreted differently.