B.D.
Is he in school? If you are concerned you can go to your dr and request a connors test. (it's written and your son doesn't even need to know you are doing it) My son 7 has add which is attention deficit disorder, adhd is attention deficit hyperactivity disorder. Those are 2 different ball games.
My son has trouble focusing in large groups, or with distractions. Since he started his medication it's been a HUGE difference. He also has an auditory processing deficicency. So he's been in an IEP with speech therapy and occupational therapy for a little over a year now.
However it's hard to test most kids untill they are about 7, because a 5 yr old does have a short attention span. If his teachers haven't noticed anything to mention to you, he's more then likely just fine.