Age 12: You can steal soda from the University of Chicago cafeteria by holding it under your opposite arm while at the counter, buying other food. The cashiers don't give a shit; I suspect this to be true of other universities. I know this because: I did it once on accident, and over 15 times on purpose.
Age 15: You can prop the doors open at my high school with quarters. Quarters are the exact length to get jammed in the door handle. I know this because: I watched someone do it.
Age 17: You can get into a bank that has credit card-access ATM only by hitting the handicapped access button. I know this because: I was locked out of work (on the third floor of a bank) and did not have a credit card.
Age 18: The only door they don't have cameras trained on at my high school is the doors out the scene shop in the theater. I know this because: I wanted soda, and needed a way out of school to get it.