Need to Help My Son Learn How to Read

My son is a very bright and energetic first grader. He loves going to school and has fun and listens well to his teachers. However, he has been having some problems with reading. His teacher is admittedly overwhelmed with a very large class, so I want to do whatever I can. I know that I need to help my son learn to read. I do not want him to be held back or be pulled out of class to see a specialist. I am looking for a program that he and I can sit down and do together to help him.