The scrotum is part of the human body, just like your arm, leg, or face. Why shouldn't kids learn what it is, and what it's called? The fact is, the age of shielding kids is over, whether the schools participate or not. And this is a good thing, IMO. Why should we be shielding kids and lying to them, pretending all this stuff doesn't exist?
I learned about sex when I was 6 years old, from another student. My parents didn't discuss it with me til I was 10, and school didn't cover it til I was 13. Doesn't that seem a bit backwards to you? Kids are still growing up thinking that sex is something unnatural and wrong, which actually draws more of them to it. It glorifies it.