California Code, Education Code - EDC § 87449

When an instructor of classes for adults serves sufficient probationary time to be eligible for election to permanent classification in that district, his or her tenure shall be for service which is equivalent to the average number of hours per week which he or she has served during his or her probationary years. In no case shall such an employee be classified as permanent for more than one full-time assignment. The service for which such a person has acquired tenure may be reduced in conformity with Sections 87743 and 87744.