Have most people on the DIS only lived in one place their entire lives?
At DS' first school (in AZ) we didn't eat with the kids. They had to eat at their desks (K and 1st grade) and there was no room for us. We could volunteer in the classroom, but that was about it.
When we moved to Belgium, we couldn't eat with the kids. Hell, at the Belgian Pre-school we weren't even allowed to go on the field trips!

Some DISers would have crapped themselves.
Now that we've moved to this hole, we're allowed. We have to sign in and we can bring them lunch. The only time I've gone is when they've invited me for Thanksgiving.