As for the principal, I wonder if he is feeling territorial, along the lines of "don't try to teach your kid, that's our job, you'll do it all wrong." (A position I find laughable given the general success of homeschooling, but a lot of professional educators hold it.) But he didn't want to come out and say it, so he fell back on the "too much screen time" trope. So, another reason not get into this with him. If I'm right, any attempt to address what he said (e.g. "this is a parenting issue, not an educational one") won't accomplish anything, because what he said is not what he meant.
Hmm, interesting perspective, and definitely plausible.
