don't they teach this at school?

I spent the weekend babysitting my cousins again. They're 13 and 16 year old boys, so by babysitting I mean "playing video games, eating chips, and farting loudly". Sunday afternoon I was driving around with Brad, the 13 yr old, and he was telling me about his 8th grade class' science experiments and how weird he thought some of them were. "So yeah," he says, "there was this one experiment and they were testing the different absorbencies of toilet paper. But I don't understand why they would do that? Why would the absorbency of toilet paper matter to anyone? Would it be for clogging the toilet?" And I say "umm it would be for girls" and he says "what do you mean?" and I say "well uhh girls wipe when they pee" and he looks at me with the most incredulous expression on his face and says "they do?????"