Cal. Education Code § 45123

(a) No person shall be employed or retained in employment by a school district who has been convicted of any sex offense as defined in Section 44010. A plea or verdict of guilty, a finding of guilt by a court in a trial without jury, or a conviction following a plea of nolo contendere shall be deemed to be a conviction within the meaning of this subdivision. (b) No person shall be employed or retained in employment by a school district, who has been convicted of a controlled substance offense as defined in Section 44011. (c) If, however, a conviction is reversed and the person is acquitted of the offense in a new trial or the charges against him or her are dismissed, this section does not prohibit his or her employment thereafter. (d) The governing board of a school district may employ a person convicted of a controlled substance offense if the governing board of the school district determines, from the evidence presented, that the person has been rehabilitated for at least five years. The governing board shall determine the type and manner of presentation of the evidence, and the determination of the governing board as to whether or not the person has been rehabilitated is final.