I think it is very important that you use the school's resources to have your son tested. By law schools (in most states) must provided special educational services to any child that resides in their district, even if the child is being homeschooled, attending a private or parochial school.
You should contact the school's counselor or principal for more information. You may also contact the board of education office for more information on having your son tested. Most districts will pay for these tests. Once the tests are completed, the school will set up a meeting with you to go over them. At that point it will be determined the type of services your child requires (if any) such as an Individualized Educational Plan (IEP), meds, etc. It is very important to have in IEP so that the school understands their responsibility in accommodating your son in his classwork and behaviors. If you son is found to have ADHD, you may want to consider obtaining a parent advocate, that can help and assist through this process since it can be very overwhelming. My son is 14 years old with diagnosis of ADHD and autism and it can be confusing, and stressful at times.
Here is a link to state and national resources. I am not sure what state you are in but hopefully this information will help.
Keep every single piece of paper you are given. Use a binder and take notes.
http://www.ptimpact.com/resources/links/state_and_national_resources.htm
Good luck and God Bless