CA has done away with all exemptions except for medical. It will be difficult to find a physician to write you one even if you’re vaccine injured, sadly. You will most likely have to homeschool
See if you can get them tested for the MTHFR gene mutation. If they have it, surely, that's on the list for medical exemptions.
Pretty sure it depends on where you live. In Oklahoma the only way is a religious exemption and you have your priest/pastor/person in charge of the church write a letter to the school.
In Canada you can get an exemption for religious OR conscience reasons i don’t know if it is the same!
I think homeschooling is your only option.