There are many people that can help you to determine if your son has ADD/ADHD, and there are many excellent treatment options that can help your son to perform well and to have a successful and normal life even if he does have ADD/ADHD. The first place to start is with a visit to his
pediatrician. There, you will be asked questions about your son's school performance, his interaction with his peers and teachers, his ability to remain focused, and other aspects of his life including how well his does in his classes.
The diagnosis of ADD/ADHD requires that there must be a pervasive (i.e., intruding) demonstration of decreased concentration, motor movements, inability to focus, etc in at least two different venues. That means, your son would need to have difficulty both at home and in school before the problem would qualify as receiving a diagnosis of ADHD. Many pediatricians will work directly with the teacher or school (and vice versa) to correctly diagnose your child and to begin the appropriate treatment regimen. There are many medications available for this common condition, and there are many resources available. Please discuss these in more detail with your son's pediatrician and his school as needed.