It shall be the duty of the principal or person in charge of the pupils in every school in the city to establish and maintain a good and efficient fire drill which shall be practiced at least twice a month during the time the building is used for school purposes. A written report shall be made by the principal or person in charge of such building of each fire drill held, and of the time elapsed from the first signal until the last person was out. (1968 Code, sec. 51-104)