okay, both of you are right and both of you are wrong.
what you're both neglecting here is that some kids develop emotionally (and physically) faster than others, while some develop slower than others. you will find 7 year olds that know a reasonable amount about reproduction, some that know a few simple things, and some that know nothing about it. there is absolutely no one-size-fits-all on the spectrum of this particular knowledge for children. i'm pretty sure all of us had at least one friend in high school who didn't know jack squat about sex, right?