An Audiologist or a trained Speach Pathologist are the ones who do this type testing. It involves the brains abilities to track more than one functional task at a time. It 's not a matter of smart or dumb it is a matter of how much sensory data {audio, visual, ect they can process at one time. I'll clue you in. Kids with allergies especially sinus allergies, child hood ear infections, or any thing over a prolonged period that effects the Inner Ear can do this. The damage is permenant. It does not go away the child has to learn coping skills.
If left untreated especially if the underlying cause the allergies ect are left untreated the more damage occurs. I reached an accute stage 8 years ago though I have had it all my life. Look for hints. Like shoes worn to one side and broke over lets say with 2 weeks to a month after buying them. Poor eye to muscle coordination is another. This doesn't hint at ADD ADHD but CAPD and the behavioral symptoms are the same. An Audiologist prescribes no medications. If a teacher suspected ADD ADHD I would ask the doctor for a complete Vestibular work up then see an Audiologist.