I'm the "real" principal, and every Spring a boy and a girl 'win' PFAD at the School Fair. They get to come up with a reasonable rule for the day, we visit classrooms, help in the Nurse's office, open the mail, do recess duty (they get their own whistle) and lunch duty (the Principal gets "free milk," which is a great perk that they love), get to answer the phone, and they "advise" me on mild discipline issues that might come up during the day. It's fun.
In addtion to the other great suggestions given, I would add:
What a wonderful opportunity for the school leadership to listen to the student body needs through the voice of a young principal for a day--let the student run (with assistance and support) a leadership meeting and ask the student to give suggestions as to what are the school's greatest needs, what needs do the student's have, what would the student do differently or what would the student keep--what a wonderful leadership training opportunity for the student. We all know that every moment is a teaching moment---I think sometimes we forget that we too can be taught.
