Picking teeth vs picking noses.

In SE Asia it is considered gauche to use a toothpick to pick one's teeth without covering one's mouth with the other hand. But it is not considered bad form to pick one's nose in public. It is also impolite to have one's head higher than a superior's head. This makes for some interesting ducking and weaving when people observe this rule as the move past seated superiors. This wasn't much of a problem for my elementary students who were shorter than I even when I was seated.