All public schools and school grounds shall be closed between 11:00 p.m. and 5:00 a.m. the following morning. No person shall be permitted on said property during the prohibited hours except for officers or employees of the public authority operating said school, and their invitees, and students engaged in school activities under the direct supervision of officers or employees of said public authority. This Section shall not prevent a person, during the prohibited hours, from passing through school grounds on a public street or sidewalk, if such exist.