Hi M.,
My son is also in fifth grade. He is quite smart, but not real motivated. He does well in all areas of school, but I have noticed his reading comprehension has gone down quite a bit.
My sister and brother-in-law are both fifth grade teachers. They advised me that in fourth and fifth the comprehension gets much more difficult, and a lot of kids drop.
There is a great website called tickettoread.com where the kids read passages and then reply to comprehension questions. That may help especially if he is more inclined to be on the computer than sit down with a book.
Also, I do not know how your school teaches, but in ours for some reason they have taught the kids to speed read and test them on their fluency and time. I have noticed that my son when reading aloud is very non-expressive and too fast. Personally, I feel that this teaching tactic has cost him in developing comprehension skills because he is too focused on being fast. When we read together, I try to slow him down and ask him to predict the future path of the story.
Taking turns reading aloud together really has helped us to bond, and I think it is helping him also with connecting to the story. It is a relaxing way to check his progress and there is no stress for either of us. I would recommend trying this. We only do a few chapters a night so even when we are running behind it is not a big impact.
Good luck.
C.