When I was in grade 5 a friend of mine had overheard the boys discussing what colour girls period blood was. They concluded that it was black since boys sprem was white and of course boys and girls are opposites!
A childhood belief about periods

others believed things like this
- I thought that the difference between girls and boys was that girls have teeth.
Anon - I used to believe all babies came out as girls and later on in life some of those girls turned into boys — Tom
- I used to believe that boys, gave birth to boys and girls gave birth to girls. How i'm so wrong now.— Sarah
- I never knew why boys had to lift up the toilet seat...until my friend told me that boys had bad aim.Anon
- I used to believe that little boys grew up to be girls and little girls grew up to be boys. — Darin
- when I was a kid, I used to believe that only girls could be my friends and all other boys were my brothers.
— rajat