(1)    On any street or highway which borders the grounds of any public, private, or tribal school in which school is held for a term of not less than 6 months, the authority in charge of the maintenance of the street or highway shall erect black and yellow “school” warning signs. The authority may also designate school crossings across any street or highway, whether or not the street or highway borders on the grounds of a school.

   (2)   All signs required by this section and their installation shall comply with standards adopted by the department of transportation.