Cal. Educ. Code § 44900

Any certificated employee having permanent classification in a district, who is granted a leave of absence and transfers to another district which is under the supervision of the same chief administrative officer or district superintendent as the district from which the employee is on leave, may acquire permanent classification in the district to which he transferred if he is employed for a second year in that district, at which time his permanent classification in the district from which he transferred shall expire.