Fourth or fifth grade is when they started teaching us about sex. By that point though, I already understood the biological reasoning behind it, just not the precise details. I remember watching a video in fourth grade with kids explaining what sex was, and they were all saying stuff along the lines of "sex happens because people really love each other," and sitting in the room thinking to myself, "No, sex happens because we're biologically driven to pass on our genes." Yes, I was in fourth grade. Yes, I thought this.