Ok, this isn't my belief but one of my friends at school...
At our secondary school, our history curriculum ONLY covered the two world wars (seriously, that was all we were taught) and didn't include any Colonial or American History.
This was when the film Independence Day had only recently been released - my friend was amazed when she saw Independence day on her calendar... only having the film to connect it to, she thought there had actually been an attempted alien invasion and the 4th of July was a commemorative holiday.
To be fair though, I only found out yesterday that The Boston Tea Party was a protest against British colonists (i'm 20), I had always thought it was a slightly less- well known music festival than Woodstock, where people had drunk tea rather than dropping acid.
It's a good job GCSE's got easier.
A childhood belief about history

others believed things like this
- I used to think that a Mormons were an alien race from a fifties sci-fi film.— Katherine
- I used to believe that an animated film meant that the film had live animals in it.— reverb
- my friend thought that the film 'the hulk' was about the jolly green giant from the sweetcorn adverts.— patticus
- I thought that wars had to last four years... just like high school and college.— A. Falk
- I used to believe that everytime a balloon was released , it meant that a child had recently died.— Samantha
- I used to think that AM and FM stood for "American Music" and "Foreign Music."— Sylvia Fowler