Lunch time is fun at my kid's school. If the weather is nice, they can eat inside or outside. Parents (or grandparents) are encouraged to join their kids. The kids all laugh and play. The lunch staff makes sure that the kids clean up their own trash, but if they help the principal pick up trash, then they get a cookie. After they are done eating, they get to play outside. It is very non-rigid.
This is an elementary school in California.
We can go home for lunch in elementary school and in high school.
I did that in elementary school and then drove to fast food or home in high school.
Forbidding this kid to talk on the phone during lunch was insane.