When I was a kid I used to get really excited whenever I figured something out in school (like the three times table) and believed that I was the only one who had figured it out. Up to this point my belief was pretty harmless but I went on to believe that I had to hide my "discoveries" otherwise the teacher would take credit for them. I ended up taking a lot of remiedial class for a year.
A childhood belief about classes

others believed things like this
- I used to think my elementary school gym teacher's name was "Jim Class".— Brandon Campbell
- When I was in elementary school I use to think that teacher lived at school at their desks all year long.Anon
- Looking back at it, the belief that dogs eat cats is a pretty funny idea. I used to believe it myself.Anon
- When I was little,I used to think the TV stopped when I went to bed. I figured it all faded to white.— Sharon
- I used to think I smelled wrong, but I figured out it was because we never used dryer sheets. — blnkfrnk
- I was sure I had it figured out: exploding turds caused farts.— al