H.M.
My daughter's birthday is in the middle of September so when she started public school we had her early-tested into Kindergarten. The testing was ridiculous but the principal saw her past preschool work and admitted her. Unfortunately, she did not learn one new thing the whole year she was in Kindergarten - it was just repetition and she was very bored. For first grade, we pulled her out and sent her to Happy Valley Charter School in the North Valley. It is a fantastic school where they group kids in classes according to their ability in each grade level. They also teach very advanced work - 2 grades above their age. My daughter is thriving there (in 2nd grade now) in spite of being one of the youngest in the class. I know they also accept kids with birthdays up until December into Kindergarten and then group them according to their abilities so that might be an option for you. Best of luck!