We have a lot of information on our site about teaching comprehension skills and how parents can help at home. The following links can help you get started on helping your son develop his skills.
If you have concerns, you may wish to discuss these with his teacher. The teacher may have strategies that work in the classroom that s/he can pass on to you. Together, you can determine the best course of action for helping your son.
Topic
Reading & Dyslexia