I can only reiterate the above post. Your son sounds exactly like my gifted/ADHD (inattentive type) daughter. I would take him to see a psychologist to be screened for ADHD as well as executive function difficulties. Our psychologist provided us with an incredibly thorough report which included recommendations for her school to implement as well as suggestions for how we could help her at home. It sounds like you'll get no assistance from the teacher even if your son does have ADHD so you may need to go the route of a 504 or an IEP to get your son the accomodations he needs. Good luck.
