The county board of supervisors, through the office of the county commissioner of schools, may establish a program of adult education and may employ the necessary teachers and other personnel, and may purchase such equipment and instructional supplies as shall be required to provide an adequate program for the education of adults residing within the county: Provided, That the board of supervisors of any county proposing to establish such a program shall first furnish evidence concerning local or county needs for adult education satisfactory to the superintendent of public instruction.