The school psychologists, here in GA, typically do not touch the subject of dyslexia.
I've been working with dyslexic kids for 8 years. My DD, who is now in college, was tested on two different occasions by the school psychologist. I was told both times that she was not dyslexic. I was told she was bright and to be patient, she would learn to read. At the end of third grade she was still at a first grade level.
I then got a private evaluation. She was diagnosed with dyslexia. I pulled her out of public school. Got trained in a reading system specifically created for dyslexics. Homeschooled her for a year and then found a private school.
Your son may not by dyslexic. If he is struggling it is in his best interests to have him tested privately.
Here is some information for you. Decoding is the ability to break down words and sound them out. Encoding (spelling) is the ability to put them back together. It has been my experience that many dyslexic kids are bright and have memorized a good number of words. It is typically around 4th grade that they begin hitting the wall. Why? Because they are running into words that they've never seen before and they don't have the phonetic ability to break them apart. Many look at the beginning sounds and the ending sounds and guess the middle.
Encoding (spelling) difficulities are sometimes hidden because the child has the ability to memorize their spelling words. They do well on their spelling tests because they have good short-term memory. Creative writing is usually difficult because they struggle with spelling.
A decoding test, usually tests the child on nonsense words. If I gave you the word TAT you would know it is not a word but in order to get it correct you would have to know the proper sound of all of the letters. The nonsense words typically give you an idea of the childs decoding abilities.
Kids who are dyslexic, or who just struggle with the whole language approach to reading typically do very well with a structured phonetic approach to learning. Phonics.
Good Luck! If something doesn't sound right to you it probably isnt'. Keep searching and keep asking questions. You are his best advocate.