My kindergarten teacher was English, so for the longest time I thought 'rubbish' was the correct word to use, not garbage, and that the letter 'H' was pronounced with a Huh sound in front of it, like Hach, not ach.
A childhood belief about speaking

others believed things like this
- I used to believe that L-M-N-O-P was 1 letter, pronounced elemenopeeAnon
- When I was in kindergarten, I used to believe that they locked the teacher's in the teacher's lounge at night.Anon
- When I was young I used to think that WHSmith was all one word, and was thus pronounced "Wwwhhhhuuusmith"— Nathan
- I used to believe that the word 'circumstances' was pronounced 'circus dancers'.— Mel
- When i first saw the word "Czech" somewhere, i pronounced it "siz-ETCH" in my head — Pachisu
- For the longest time I thought 90210 was a sitcom Anon