@samiest You posted your original question on the homeschooling forum. As homeschooled students, as the parent, I decide what my kids take. If I have a young student ready for college level material, I make the decision, not school administrators. Lots of homeschooled kids start dual enrolling in college based on ability, not age. Students dual enrolling take college level classes as high school students, so they are earning college credit and their high school diploma simultaneously. How that works in individual states differs. I don’t live in CA, so I cannot speak directly toward CA law.
Have you investigated the accelerated student resources in your area? Math circles? Art of Problem Solving courses? Or AoPS forums (good place to ask questions)? Online local groups for gifted students? I know several families through online groups with extremely advanced kids who live in CA and homeschool. One has a ds who was just accepted to Berkeley as an UG at a very young age. The student had completed multiple upper level math courses before he was even a teen. Another’s ds scored a 5 on BC at age 12.
But what you are able to do within the school system, I have no idea. You need to redirect your question to a different forum if your student is in public school.
Fwiw, students can DE at Berkeley. http://extension.berkeley.edu/search/publicCourseSearchDetails.do?method=load&courseId=4606656 How that works for ps students, again, I have no idea.