Before I entered kindergarten, I used to believe that 11 and 12 should have been eleven-teen and twelve-teen.
Why not? There's thirteen, fourteen and so on...
I figured the entire group should match. :-)
A childhood belief about counting

others believed things like this
- in kindergarden i beleived that to be a teenager your name had to end with teen— eric
- until I was thirteen I used to believe that "homocide" was two homosexuals killing eachother. Anon
- When I was nine, I thought two eleven-year-olds could get married.Anon
- When I was a little kid i thought cattle meant a group of cats— It's a group of cows and bulls!
- My cousin used to think that a group of nine singers was called a "niner".Anon
- i used to think that the paparazzi were a group of Italian criminals or spies. i have no idea why?? Anon