ADHD, Attention deficit Hyperactivity disorder, is not necessarily correlated with IQ testing. There is no specific neuropsychiatric test that is diagnostic of ADHD; it is a clinical diagnosis. There are three types of ADHD: inattentive type, hyperactive-impulsive type and combined type. From your description your son may have inattentive type. Neuropsychiatric testing can be helpful to clarify different reasons for poor academic performance but a good history is the main diagnostic issue. Please discuss these results with your pschologist and physician for further clarification.