If I'm anywhere except at home, I usually pick my nose in the restroom while I'm washing my hands. I even do it now as an adult, and no one cares. I pick boogers to until my nose is nice and clean, then rinse my hands. Even when I did it in high school, no one gave me dirty looks because of that. But in elementary school, before I learned that I was violating some very serious unwritten rule, I was bullied mercilessly for trying to get rid of an uncomfortable feeling in my nose. So here's my advice to people in school: if you must pick your nose at school, do it in the restroom only; it's also semi-acceptable to do it while showering after gym, just be discreet about it. But don't do it in class, in the hallways, during recess, and especially during lunch.