Sexy Fun Times/Work/Doctor/Sex Ed
The class is small; only twelve children - seven girls and five boys. Of course, private school classes tend to be smaller anyway, but some of the kids have parents who think it's better they kept in ignorance. This is not the first time you've taught them, so they already know the theory; now it's time for something more practical.
You put the first slide on the screen; it's a picture of two naked children, aged about eight or nine, standing up and facing the camera. "I guess you're all pretty familiar with your own bodies, but some of you, especially those without siblings, may not know much about the opposite sex." You switch your laser pointer on and indicate the children's chests. "Your notice that there is virtually no difference between the boy's chest and the girl's chest at this age. The age at which girls breasts start to develop varies, but I expect that some of the girls in this class are already showing signs."
You switch to the next slide which shows the same children but as a close-up of their genitals. You hear a snigger from one of the boys but choose to ignore it. You point at the boy's cock. "You can see that even at this age the boy's penis is quite well-developed, but his testicles, although they are there, are not yet producing any sperm. You might wonder why they're on the outside; that's because they need to be kept cool. It must be quite warm a studio where this picture was taken, because you can see how, even at his age, the boy's scrotum has expanded to get his balls as far away as possible. If it was cold it would shrink."
You switch your pointer to the girl. "Girls, especially girls this young, don't have very much on view; all you can see when she's standing up like this is the slight bump of her pubic mound above a slit." You switch the projector off. I think that's enough pictures for today; you've all seen the drawings and diagrams anyway, so now I think it's time for you to see the real thing.