I used to believe that your age was the same as your grade. For example: if you were 1 you'd be in first grade, if you were 2 you'd be in second grade and so one.
A childhood belief about classes

others believed things like this
- A[n] nth grade teacher only had to finish the nth grade when he or she was in school.— MD Caruso
- When I was in 3rd grade, I used to believe that M&M's took away headaches.— enid
- I used to think, all the way up to eight grade that if you smoked cigarettes you were an alcoholic— praneeth
- Up until the 5th grade, I thought that all Egyptians were extinct. — Amy x
- From preschool to 1st grade I thought that every boy had a "henis."— I know what they're called now
- 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