At school it can cause problems, as a lot of importance is placed on reading and writing.
If nobody realises that you have dyslexia it may seem that you are not very clever or just being lazy - this can make going to school very upsetting.
Tom Cruise has said about dyslexia: "My childhood was extremely lonely. I didn't have many friends. I was dyslexic and a lot of kids made fun of me. That experience made me tough inside."
Noel Gallagher also has it: "I have problems with words over six letters long. School days were the worst days of my life."