California Welfare And Institutions Code Section 11403

A child who is in foster care and receiving aid pursuant to this chapter and who is attending high school or the equivalent level of vocational or technical training on a full-time basis, or who is in the process of pursuing a high school equivalency certificate, prior to his or her 18th birthday, may continue to receive aid following his or her 18th birthday so long as the child continues to reside in foster care placement, remains otherwise eligible for AFDC-FC payments, and continues to attend high school or the equivalent level of vocational or technical training on a full-time basis, or continues to pursue a high school equivalency certificate, and the child may reasonably be expected to complete the educational or training program or to receive a high school equivalency certificate, before his or her 19th birthday. Aid shall be provided to an individual pursuant to this section provided both the individual and the agency responsible for the foster care placement have signed a mutual agreement, if the individual is capable of making an informed agreement, which documents the continued need for out-of-home placement.