To help a fourth grade child with reading comprehension, do reading activities, such as code cracker, with him. Sign him up with a tutor or a private reading program.
For code cracker, write down the alphabet on a sheet of paper. Write a code of letters underneath the alphabet. One simple code is changing the meaning of each letter to the letter one or two places behind it in the alphabet, with the first letters looping back to the end of the alphabet. In a code like this, the letter "c" could mean "a," while "a" would mean "y." Write messages for your child to decode, then have him write messages back.
As of March 2015, SmartTutor.com has a free reading comprehension game called Story Structure. Visit the Smart Tutor home page, and place your cursor over Free Resources. On the drop-down menu that appears, place your cursor over Free Reading Lessons, then click on Fourth Grade on the next menu. Click on Story Structure Level 4 Vol. 1 to play. The game teaches children about story elements and allows them to design their own story.
A child may not be motivated to read. In this case, an incentive program can help. Tutoring and reading programs typically have incentives as part of the program.