I grew up in a condominium complex full of kids of all ages, so information quickly trickled down through us all. Like, I don't remember ever -not- knowing what sex was. I found out when I was four or five? Maybe earlier?
As for sex toys, I think I was eight or so when I found out about those. The first time I saw one in real life was when I was about ten or eleven. I was trying to pull something I dropped out from under my parents' bed and wound up touching something where I saw nothingness. (It was dark under the bed and it blended in.) I pulled it out and at first, I just thought it was a black tube. Then I noticed the veins. And I quickly shoved it back under the bed and left.