Cal. Health & Safety Code § 104850

Treatment shall be provided for a person only if the parent or guardian or responsible relative or adult who has assumed responsibility for his or her care and custody (in the case of a minor), or the person (if an adult), files with the governing board of the school district or the governing authority of the private school, as the case may be, a letter provided by the district or authority pursuant to Section 104855, stating that such treatment is desired.