Sexual education should not be taught in kindergarten.
Would that also exclude teaching small children how recognise (risk of) sexual abuse?
No I don't really consider that sexual education. I was more referring to sex positions, nerve endings, secretions, forms of protection, cross dressing, and homosexuality. It's always good to teach of abuse.
So what ages do you think should learn sex ed - after all, you only said kindergartners in your first post? I don't think kindergartners should be learning about sex positions and condoms and things, but I think older kids should be learning them. Also, why shouldn't kindergartners be taught about "cross dressing and homosexuality"? They exist and they're totally harmless.
Making sure people of reproducing age have a basic understanding of what the forms of birth control are, how they work and where they can be obtained is an integral part of any rational public health policy.
I'm not sure why anyone needs to learn about "sex positions" in school. I think that's more a matter of trial and error.