While I appreciate your caution, you still have some reading to do but I would not wait to get him assessed while you are still learning. Most people are also going to tell you that a psychologist or psychiatrist is not necessary, go to a medical doctor. At 15 you need to ask your son whether he is more comfortable with a pediatrician than you or your husband's doctor. My stepson had ADHD and it was obvious. My daughter has ADD and it seemed more like a defiance, behavioral issue when it was simply the ADD. Many children with ADD do fall through the cracks because without the hyperactivity, many go undiagnosed.
It is a chemical imbalance and if he has ADD, it IS a quick fix because the only thing that corrects the chemical imbalance is medication. Some people believe that the child can "learn" to cope without meds but a psychologist once asked me if I would withhold diabetes medication from my child, which is exactly the same thing, it corrects a chemical imbalance too. If he has ADD and you continue to drag your feet, it is longer that your son feels stupid and/or like he is a bad kid, struggling just to maintain minimal standards for acceptable behavior, really for nothing.
Also recognize that not all kids are going to display all of the characteristics. All they do when they diagnose this condition is to have the teacher and the parent fill out forms about the child's behavior. When there are enough of those behaviors that fall into ADD, that is the diagnosis.
There is apparently some type of imaging that can now be done to diagnose that I saw a clip on Good Morning Texas this morning so I would go to the website and start googling. From what I caught, it allowed them to see exactly what this girl needed in terms of medication which allowed them to manage the condition much better.
The medication is essentially a stimulant so it is pretty easy to determine whether a kid is misdiagnosed. Ironically, when the child needs the medication, a child with ADHD will be able to slow down and focus and a child with ADD will be able to focus. If the child is not ADD/ADHD, the meds will have him bouncing off the walls.
Contact the child study center and don't be insulted but I think you are struggling with dealing with your child not being perfect. If I have misread, I apologize but you seem so serious and grave about this and whether it is ADD or something else, you will figure it out. The important thing is to fix things as quickly as possible and don't buy into the people who try to claim you are a bad parent for doing what a good parent does which is treat the child's condition.
