Pretty sure Joerocket's hit it on the nose there, gregma.
I disagree: (9.41.280)
(1) It is unlawful for a person to carry onto, or to possess on, public or private elementary or secondary school premises, school-provided transportation, or areas of facilities while being used exclusively by public or private schools:
unless it is a public or private elementary or secondary school premise... I don't think you could consider the offices that handle payroll to be a school premise... I could be wrong on that, but, if the intent of the statute is to keep kids safe... then how does the administration building have anything to do with guns being near kids?... seems odd and I doubt that you would lose in court... that said--I don't want to be the test case but probably wouldn't be too concerned with carrying concealed. Anyway, IANAL