California Code, Penal Code - PEN § 627.2

No outsider shall enter or remain on school grounds during school hours without having registered with the principal or designee, except to proceed expeditiously to the office of the principal or designee for the purpose of registering.  If signs posted in accordance with Section 627.6 restrict the entrance or route that outsiders may use to reach the office of the principal or designee, an outsider shall comply with such signs.