California Code, Education Code - EDC § 44960

The services of any permanent certificated employee referred to in Section 44959 who has been appointed to substitute service in place of another employee who is on leave of absence for civilian or military war service may be terminated upon the return of said other employee from such leave of absence, but only at the end of the current semester or quarter and not less than 30 days after written notice that his services will no longer be required.