Cal. Educ. Code § 16203

Not later than July 10th of each year the county superintendent of schools of each county in which there is a school district maintaining facilities for the education of exceptional children which have been constructed with funds apportioned to the district under this article shall certify to the board of supervisors and to the county auditor of the county the total number of units of average daily attendance of pupils enrolled in the facilities during the next preceding fiscal year who reside in a district other than the district maintaining the facilities. On or before July 10th of each year the county superintendent of schools shall notify the governing board of each affected school district of the total number of units of average daily attendance of pupils residing in that district who were in attendance at the facilities maintained by another district.