California Code, Education Code - EDC § 22516

(a) Nothing in this chapter shall be construed or applied to exclude from membership in the Defined Benefit Program any person employed to perform creditable service at a level that requires mandatory membership in the program for which he or she has the right to elect membership in the program or another retirement system and who elects membership in the other retirement system, or who is employed to perform creditable service at a level that does not require mandatory membership in the Defined Benefit Program.

(b) Service performed after becoming a member of another retirement system shall not be credited to the member under this part, nor shall contributions or benefits under this part be based upon that service or the compensation received by the member during that period of service, except as provided in the definition of “final compensation” contained in Section 22134or 22134.5.