When I was in the first grade I was told that wearing rubber galoshes in school was bad for your eyesight, and I believed it. (I'm still not sure it isn't true.)
A childhood belief about eyes

others believed things like this
- I believed that the word optimistic was something to do with opticians and being happy with your eyesight.Anon
- My dad told me that the reason Birds didn't get electrocuted on overhead wire was they had rubber feet!!— Derricki
- A[n] nth grade teacher only had to finish the nth grade when he or she was in school.— MD Caruso
- I had an 18 lb. cat who ate rubber bands, I used to believe she could bounce away if not careful.— Dawn
- When I was a child, I used to think that one day my brother and I would be in the same grade at school.— Alexis Yahir López
- I used to believe that your brain was a red rubber ball inside your head.— Greg