I linked to the superintendent of schools earlier but here it is again
YouTube - Prop 8 has nothing to do with schools
Of course Prop 8 didn't have anything to do with schools. I think the contention was that gay marriage would be taught in schools if gay marriage is allowed to remain legal.
Here's where it says in no uncertain terms that parents can opt out (sorry for leaving that out).
15."Do parents and/or guardians need to be informed if their child is to receive sex education or HIV/STD instruction?
Yes. The law recognizes that while parents and guardians support the teaching of medically accurate, comprehensive sex education in schools, they have the ultimate responsibility for teaching their children about human sexuality; they may choose to withdraw their children from this instruction.
EC sections 51937 and 51938 explain that parents or guardians must be notified (passive consent) by the school at the beginning of the school year about planned comprehensive sexual health education and HIV/AIDS prevention education, be given an opportunity to review materials, and be given the opportunity to request in writing that their child not participate in the instruction."
...
Parents must be notified of any planned assessments, be given the opportunity to review the assessments and, in grades seven through twelve, and be given the opportunity to request in writing that their children not participate. Prior to seventh grade, parents must give their active consent in order for their child to participate.
Fair enough. There is still a problem. Those parents' tax dollars still go towards funding the school, and probably the sex-ed program, also. They still have the right to say what they want their tax dollars funding, even if they can opt their children out.
Frequently Asked Questions - Comprehensive Sexual Health & HIV/AIDS Instruction (CA Dept of Education)
I misread the part about it being only for middle schoolers, but it does say age appropriate and it only mentions respect for marriage will be taught.
Although I guess the burden of proof is on your side that it will be taught to elementary schoolers or kindergarteners. I haven't read anything official that would suggest this.
Depending on the school district and when they decide to teach it, sex ed can start in 5-6 grade. At least, where I'm from. Then again, it might be different in CA. since I don't know if their elementary schools still go to 6th grade, or even 7th grade.