Looks like the clearest route (see excerpt from CDE below) is enrollment in private K for a year, followed by admission to public K according to age, with immediate promotion to first on district & parent agreement.
First Grade Enrollment
California law requires a child to be six years old on or before September 1 for the 2014–15 school year and each school year thereafter to be legally eligible for first grade EC Section 48010.
A child who was legally enrolled in an out-of-state kindergarten for one school year (using that state's requirements), but who does not meet California age eligibility for first grade, may, with parental consent, be enrolled by the district in first grade (EC Section 48011).
A child who was not age-eligible for kindergarten (that is, the child turned five after September 1 in the 2014-15 school year or thereafter) and who attended a California private school kindergarten for a year is viewed by the CDE as not legally enrolled in kindergarten, pursuant to EC Section 48000 requirements. Therefore, this child, upon enrollment in public school, is enrolled in kindergarten, assessed, and may (but is not required to) be immediately promoted to first grade if the child meets the following State Board of Education criteria, pursuant to Title 5, Section 200:
The child is at least five years of age.
The child has attended a public school kindergarten for a long enough time to enable school personnel to evaluate the child's ability.
The child is in the upper 5 percent of the child's age group in terms of general mental ability.
The physical development and social maturity of the child are consistent with the child's advanced mental ability.
The parent or guardian has filed a written statement with the district that approves placement in first grade.
A statement, signed by the district and parent/guardian, is placed in the official school records for these five-year-olds who have been advanced to first grade (EC Section 48011). This action prevents a subsequent audit exception for first grade placement of an age-ineligible student.
Considerations. Young children who are placed in kindergarten or first grade may feel stress as they try to achieve academic expectations and relate to older children. Parents/guardians and early childhood educators are the best judges regarding what may be gained by acceleration and whether it is worth the price. CDE recommends that educators and district employees explain to parents/guardians of under-age children the following:
The academic, social, physical, and emotional readiness required for kindergarten or first grade
The rigorous nature of the academic standards
The potential for harm to a child's disposition to learn by inappropriate acceleration, and,
The important concepts, skills, and knowledge imparted at each stage of a child's education, including preschool.
Often it is helpful if school or district staff members arrange for parents/guardians to read content standards for kindergarten through first grade, visit classrooms, and observe instruction. Districts may provide additional information for parents/guardian.
