I receive questions nearly every day about testing for dyslexia - questions such as "Does my child really need to be tested?"; "How can I get the school to test my child?"; and "Why doesn't my child qualify for services at school?"
I recently found this article and I think it might answer some of your questions.
Suspect Dyslexia? Here are some tips to prove it, by Kelli Sandman-Hurley, Ed.D.
