It shall be unlawful for any person or persons to remain, stay or loiter in or upon the grounds of any public school in the City of Anaheim between the hours of ten-thirty p.m. and five a.m. of the following day unless authorized in writing to remain on said public school premises by the school principal or his authorized representative. As used in this section, "loiter" means to delay, linger or to idle about without a lawful purpose for being present on said public school premises. (Ord. 3402 § 1; March 4, 1975.)