The board of county commissioners may authorize employment of school guards for the sole and only purpose of directing travel and traffic on streets and highways outside the limits of incorporated cities and towns whenever the board deems it necessary to protect the life and safety of pupils attending the public schools of this state. School guards so employed shall meet the qualifications, perform such duties, and have such tenure as prescribed by the board of county commissioners. The school guards shall be paid a salary fixed by the board of county commissioners and shall be paid from the general fund as stipulated by the county excise board.