And until the kid does reach that sophisticated age, I'd probably just say, "We have to follow rules for our safety like not standing on tables, and we have to listen to teachers/lunch aides/administrators, but you already had your punishment at school, and that is enough."
I was being a bit flippant, obviously-- I'm pretty much a hardliner about following rules that are about the safety of the greater good. When the kids were little and full of the eternal "Why?" (Which, actually, they still are, but for different reasons) my answer would be phrased back at them in the form of a question that was designed to make them think. In this case, it would've been something along the lines of "Well, what do you think would happen if everyone stood on the tables and started singing and ignored the teachers?"
Generally, they'd figure out why that wasn't such a good idea on their own, so I figure it was an approach that worked at least the majority of the time. Nate, in particular, was singled out by his teachers this quarter as being an exceptional role model for the younger kids which, as you might guess, made me a seriously proud momma.