My cruel older brother decided to tell me one day when I was four that Madagascar was uninhabited because it had a very active volcano and man-eating monkeys to boot.
I, of course, believed him and would tune out in elementary school when they tried to teach us world geography and mentioned Madagascar (because it obviously didn't matter). It wasn't until I was in 6th or 7th grade that I actually stopped to think about it and realized I was wrong!
A childhood belief about places

others believed things like this
- I used to think that a car boot sale was where motorists exchanged car boot lids.— Alan, Sheffield, UK
- When I was in elementary school, I believed my heart moved across my chest throughout the day.— Allison
- 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
- When I was little I thought grown ups could fly but wouldn't tell me about it or teach me until I got older.— James the Great
- My little brother was afraid of toliets cuz he thought monkeys would jump out of his butt.— ~~~ Crazy Bro ~~~
- When I was in elementary school I use to think that teacher lived at school at their desks all year long.Anon