I wish I lived in Cali to vote No on this, but I'm on the other end of the US.
I mean, anybody should be able to marry the partner of their choice. What happens behind closed doors is not really my concern, or anyones. Unless it something like murder... /random tangent.
I honestly don't think schools are going to teach about gay marriage, even if it's legalized. At least not THAT early. Hell, I've known about gay people since I was like... 10 or so (My father), and it's never hurt me in any way unless you count the whole... getting ridiculed in school and morons saying "You're dad is gay, so you HAVE to be gay, I'm gonna beat you up now because of this".
If you ever discover you are gay, and your parents learn about it, your parents are likely to like, DISOWN YOU or something.
Depends on how accepting vs. homophobic your parents are. When my brother came out, my parents were basically "We sort of expected you to turn out like this..."
Good luck though, Doozer