When I was in gym class at school I always thought they told us to stand "shoulder with the part" and I remember thinking "what does that even mean?" and just looked at what everyone else was doing to figure it out. I was much much much older when I had the epiphany that it's shoulder WIDTH apart, which makes perfect sense.
A childhood belief about classes

others believed things like this
- At the age of about 5, I thought that any man carrying a bag/sack over his shoulder was a burglar.— Police officer, Ola.
- I used to think that the shoulder blades were actually "back breasts".— Kdees
- I used to call the shoulder of the road, the elbow.Anon
- When we were younger my sister and I used to think that our shoulder blades were really sprouting wings.— Raven
- I thought the lines in the sky left behind by airplanes were "sky scrapers". Makes sense.Anon
- I used to think that girls' anuses were green. I remember thinking that as late as high school.— Jack