I suggest you read Homeschooling: The Teen Years by Cafi Cohen.
You'll find a list of independent study programs that may work for your kids if you, a relative, or a friend are willing to provide the necessary help and support they require. Another option is to contact the Homeschool Association of California. Perhaps they are aware of other programs in your area that can accommodate your children. Ask for their free 32-page guidebook for new homeschoolers. You can call them toll-free for more information: 1-888-HSC-4440. Good luck!