The county superintendent of schools may, with the approval of the county board of education, employ personnel to provide necessary guidance services to pupils in elementary school districts under his jurisdiction which had less than 901 units of average daily attendance during the preceding fiscal year, in high school districts under his jurisdiction which had less than 301 units of average daily attendance during the preceding fiscal year, and in unified school districts under his jurisdiction which had less than 1,501 units of average daily attendance during the preceding fiscal year; provided, adequate guidance services are not being furnished by the district.