I must admit, everyone's experience here is vastly different from my own. Being sexually aware at 10 years old is baffling, as in my neck of the woods, we didn't start dating seriously until after high school. There were a few kids who had boyfriends/girlfriends during high school, but they were more buddies who kissed more than anything else. We saw that as kinda odd, really - probably because most of us weren't in the mindset of having sex and being intimate with another person.
I remember being confused at teen movies, about the stereotype of teenagers having sex on their minds 24/7. In our school, we just didn't bother with it. That's not to say it wasn't present. We had sex-ed (with the condom-banana demonstration and everything), watched the videos, studied the flash cards of STDs, and of course made the dirty jokes. We were aware of it, the ramifications, the pleasures, everything - we just didn't concern ourselves with it. We also had a version of sex-ed in the second grade, that didn't really talk about sex, but dealt with anatomy. We were taught the medical names of genitalia, and the main lesson was that if anyone tried to touch you there, you could specifically identify that this person had touched the scrotum/vulva/breasts/anus. We tittered about it as 7 year olds, but looking back, I think that was very empowering and I love that no parents had an issue with it.
That's not to say there we didn't have sexual peers. There was a boy who was having active sex at 13, which really threw us seventh graders off, and a couple high school girls that were pregnant. Also, there were girls who dated older boys and were more mature and experienced about sex.
It's interesting to see other views, but my point is that most of my peers and myself would have been grossed out about being actively encouraged about sex at 10 years old in the fourth grade. Not because of shame or conditioning, but because we personally weren't ready for it yet. We had the knowledge, and generally knew it was okay, but we didn't think about it seriously until much later. If YOUR 10 year old can handle it, and is actively curious, of course talk to them more explicitly about it. Otherwise, though, I think it can be left off for a while, with just the essentials birds and the bees.