Please go to your local public K's website or call them for a copy of the K curriculum so that you can set your expectations correctly. If your child is advanced and PG, you may be surprised that the K curriculum is not much different from an average preschool curriculum (in the "strong" school districts in CA). They talk about "number sense", finger strengthening activities like coloring, art, craft, sight words, rhyming words and maybe, if your school district is very strong, they might do a few hands on science experiments and a few field trips.
What we needed from them was help with learning to write legibly (which was my DS's weakness), but they never taught how to write the letters correctly and instead gave them sheets of paper with letters to trace without monitoring or helping them.
I suggest that you have a backup plan in case you choose to send your child to public school - which was after schooling in our case. We taught from curriculum and used many online programs like Dreambox, EPGY etc.
We then switched to a rigorous private school that accelerates DS in Math, Science and LA. We feel that he finds the math too easy, so we after school math now.
Testing at 4 is a good option - it shows you what the strengths and weaknesses are at an early age.
