California Code, Education Code - EDC § 35033

If a unified school district is formed pursuant to Chapter 2 (commencing with Section 4200)   1 of Part 3, of Division 1 of Title 1 to include all the territory of one or more elementary school districts, the governing board of the unified district may elect and reelect as district superintendent of schools of the unified district, or as deputy, associate, or assistant superintendent of schools of the unified district, for a four-year term, a person employed as district superintendent of schools of one of such elementary school districts at the time of the formation of the unified school district.  The person may perform service in the position for the unified district for the term to which he is elected or reelected without possessing the certification document otherwise required if he has served continuously as district superintendent of the elementary district for at least 10 years prior to the formation of the unified district and if he is elected as district superintendent of schools of the unified district or as deputy, associate or assistant superintendent of schools of the unified district pursuant to this section.