There has developed this consensus over the past few years (which you also see reflected here on HN quite a lot) that school is essentially pointless and waste of time. If that is what you as a parent believe, then why should you take it seriously or care about what rules or wishes the school has?
I know there are autodidactic folks, but I would know substantially less basic math, biology, chemistry, English, and history if I hadn't gone to grade school.
Possibly, but parents/elders coming to have lunch their child/family member is a pretty common practice. Not every day, for sure, but I always thought it was great whenever my older sister or parent/grandparent came to visit me for lunch when I was younger. I'm sure they coordinated with the office, it's not like they just showed up out of the blue. I would hope the world hasn't changed that much, but maybe it has
Anecdote: a client went to see their daughter, and their classmates approached him and hugged him, and this was seen as highly inappropriate, and they ended up having to move schools. That was California.
I'm in my 30s and in the Southeast so definitely a different world, positively and negatively, but I don't see how that's inappropriate unless he forced the classmates into hugging him or made some kind of scene.
That's the thing, with context, it doesn't seem inappropriate, especially as kids approached him, and I would almost argue that the failure was on behalf of the school for letting someone walk in and be near kids, but they didn't see it that way.
But in today's climate, they informed the parents what happened, they socially ostracized him and his daughter, assumed the worst because they were denied the full context of intent.
If you want to see your kid, come have lunch with them one day or something like that