One day in class, we had gotten very off-topic, as we often did in this class, and we arrived at the topic of chickens. The teacher raised chickens for the eggs, to sell and eat, and it happened that he had an incubator full of eggs in the classroom.
One boy asked if any of them were roosters. The teacher responded by rhetorically asking how he'd know, before the eggs were hatched. Then, one girl, looking confused, asked why a rooster would come out of a chicken egg in the first place! Another girl sitting next to her whispered something to her, and she said... "Ohhhhh, I get it..." and turned bright red...
By the way, how old did you imagine these kids were? And what sort of class did you imagine them in? No, not elementary school -- this was 10th-grade physics class. Really.
A childhood belief about birds

others believed things like this
- I used to believe that only brown eggs came from chickens. I thought white eggs were made at the store— Destiny
- I used to think my elementary school gym teacher's name was "Jim Class".— Brandon Campbell
- I used to believe that like chickens lay eggs, pigs laid sausages...Anon
- I believed that chickens pooped eggs (male and female)— WHAT-A-Doodle-WHO??
- My partner's Mum thought that pigs layed sausages just like chickens lay eggs.— Bunny
- I used to beleive that eggs were actually poop from chickens, and that eating it would make you throw up.Anon