I am an adult dyslexic with a BS in aerospace engineering and an MS in Technology Management and a fine career in spacecraft flight operations. When I was in third grade I could not read or write anything. Not even words like "it", "the" or "cat". My teacher told my mother that I was probably retarded. Mom said, "No" and sought out training.
Yes I had very serious behavioral issues. Unlike many of the behavioral issues brought up in this website, mine were not of a medical nature, they were environmental. I could not learn the way the school taught me, and was tormented by the kids, picked on by other frustrated kids with learning disabilities, humiliated by the teachers, and severely punished for not doing what I could not do. I was angry and had no self esteem. I hit my all time life low in 3rd grade.
What saved my life are two things: 1) Orton Gillingham training, 2) a child physiologist that understood the emotional issues of being a dyslexic child in a school environment not equipped to deal with it.
Dyslexia really means someone of normal or high IQ that has a difficult time learning to read and write in a traditional classroom environment. That's it. There are as many reasons for a person to be dyslexic as there are dyslexic individuals. Research has shown that the most effective techniques are based on a structured multisensory phonemic awareness approach. Orton Gillingham was the first such program. There are dozens now. The IDA can provide you with a list of approved programs. Wilson is one. Programs like "Reading Recovery" and "Hooked on Phonics" have good stuff in them, but go to fast and not deep enough for the dyslexics kids. So they don't work that well.
I have three sons, two inherited my reading issues. Our schools did not recognize the term "dyslexic" they used Learning Disability (LD). But I don't care what you call it, just provide the proper training. When I pushed for what training program the school was going to use, they provide me with a book list. They did not even know what a training program was!!!!!!!!! I found a private OG tutor, and the school was amazed at how well my first child did. (After a couple of years of blowing me off they started respecting me)
I was smarter when my third son started having troubles. By then I had learned that strong phonemic skills started at age 3 were the most effective way to compensate. He had the most significant issues, but started young enough that now he reads better then any of us.
Me: Now I read and compose at a graduate level. But, still struggle with spelling. No feel for it at all. I believe in myself - and that made the biggest difference.