If there isn't a branch of CHADD near you, then try the Learning Disabilities Association of America at 1-888-300-6710 or the Coordinated Campaign for Learning Disabilities at 1-888-GR8-MIND. These organizations are extremely helpful to parents in providing information and support and in making referrals for diagnosis and treatment. They will also give you advice about your legal rights to an appropriate evaluation.
Second, ask CHADD, your pediatrician, or school guidance counselor/psychologist for a recommendation for a professional who can do a full evaluation for your sons. The school must do an evaluation if a parent requests it (put your request in writing), but they are rarely equipped to make a diagnosis for ADHD. They can identify any learning problems your sons may have, however, and make a recommendation for support services in the school if necessary (many children with ADHD may also have learning disabilities or related social-emotional problems). Even if a psychologist or other related professional makes the diagnosis of ADHD, he cannot prescribe the medication that may be called for. Only a medical doctor can do that.
Third, there are a number of wonderful resources for parents of children with ADHD that you might want to have a look at. I would recommend:
Taking Charge of ADHD: The Complete Authoritative Guide for Parents by Russell A. Barkley
Dr. Larry Silver's Advice to Parents on ADHD (2nd edition) by Larry B. Silver, M.D.
Problem Solver Guide for Students with ADHD by Harvey C. Parker.
You do not have to go through this process all alone. There are many resources available for you and your children. Good luck!