Many successful people were dyslexic. Richard Branson and Einstein are two from memory.

The tests they use to diagnose developmental dyslexia are just an age appropriate IQ test where if the person is above average in most areas but is below average in areas like short term memory recall, simple maths, reading out aloud or sounding out new words. Perhaps the child isn't dyslexic, but is shy or was never taught simple maths like long devision. Sometimes children miss something in class and never catch up. I remember missing the class on how to tell the time with an analog clock. My grandparents ended up sitting down and explaining it to me then it finally clicked.

A few people in my family were "diagnosed" with dyslexia from these tests. My dad can't remember a phone number but can do complex maths and studied engineering. My sister was diagnosed early and was schooled at home, finishing last year. University isn't an option for her like the rest of our family, but that's not that big a deal. She has missed the social aspect of school the most.