My mom was called stupid her entire first school years until somebody thought to test her eyes.
I was 12 when I first saw a leaf on a tree.
I had an eyetest in primary school, I couldn't read anything. Looking back on it years later I assume she thought I was joking or else just royally cocked-up!
It left me with some strange cognitive coping strategies - like I would always dictate what the teacher was saying rather than reading it off the board.
The offshoot is I have very poorly formatted but fast handwriting!