Kindergarteners are you kidding me? I thought that was a joke.
But I do have to say in the public schools that my kids are in sex ed is introduced in Jr. high with a follow up in 9th grade. The parents must sign a waiver saying they can take the class. The majority of kids take it. You are made fun of if you don't take it because it is very obvious you are suddenly gone from PE. They separate the girls from the boys and for some this is the ONLY sex ed. these kids will ever hear about. So I feel if you have an open relationship with your kids the parts you don't agree with can be reiterated at home.