Cal. Educ. Code § 1730

The county superintendent of schools may, with the approval of the county board of education, employ supervisors to supervise instruction in the elementary school districts under his jurisdiction which had less than 901 units of average daily attendance during the preceding fiscal year and in the elementary schools of unified school districts under his jurisdiction which had less than 1,501 units of average daily attendance during the preceding fiscal year. The services of supervisors shall be made available in such elementary and unified districts in which adequate supervision of instruction is not being provided by the district.