The Individuals with Disabilities Education Act (IDEA) is a federal law that is designed to provide special education services to children with special needs. Each state has a mandate to provide services in accord with this law. So your son can be evaluated for the purpose of determining if he displays a learning disability. Speak with staff in your local school district about this. My sense from your note is that your son should not be home schooled. Relative to the possibility of ADHD, the evaluation should be done by a pediatric mental health professional. Ask your son's doctor how to go about this.
Your state, under federal law, has the obligation to "not leave your son behind". You need to contact your local school district, in writting, and inform them that you need your son tested for learning disabilities, including ADHD. I am surpirsed that they did not do this when you had him in school. They will test him free of charge to you and develop a plan to best help him. If you do not agree with the results of their evaluation, the school district has to pay for a second opinion. You are not a teacher and should not be trying to do this on your own. If you can afford or have insurance, you also/ in addtion to the school district should get a private evaluation for these issues as the doctor stated. How is his speech and social skills with his peers? Does he play well with one or two other children? Can he speak well for his age? If he has speech and social skills issues in addition to control and academic issues he might have PDD or PDD-NOS with or without ADHD. I am not a doctor and a doctor that specializes in child development can evaluate him for all of these disabilities and tell you how to best help him. Good luck and be an advocate for your child always.