Your child’s not understanding what he reads is a serious problem. In fact, it may be the single most important sign of learning and school problems. It can have several causes.
Vision problems go at the top of the list. For children in school, undiscovered vision problems are not very likely. Illness, difficulty concentrating and paying attention, not liking what is available to read, and finding the effort required a bit much also are possibilities. Here is the key idea. Not understanding what he reads has little to nothing to do with not trying, being lazy, or a bad attitude. These kinds of things could cause your child not to read; but they have nothing to do with understanding or not understanding. When this sign is present, your child goes through the motions of reading. It just does not lead to understanding.
If you ask your child to read a page from one of his school books and he looks at all the words, he has gone through the motions of reading. You then ask a question or two and discover he does not understand. What is happening? Here is what to think about.
Your first idea may be he is not smart enough to understand. Maybe he does not know some of the new words. He may not know anything about the ideas or subject area. Any of these problems could cause him to have trouble understanding. They should be checked out. But the problem usually has little to do with these kinds of things. It is more likely he has a reading disability.
What is a reading disability? There are several kinds. They sometimes involve perception: your child sees what is on the page but has trouble making any sense of the marks and squiggles. Your child may see things backward or upside down. He may be unable to track the line of print across the page. He may have problems keeping oriented on the page. A reading specialist can help define the problem(s) and suggest ways to help him.
Keep this point in mind. Children who can learn usually do learn. Youngsters who can read and understand usually do. If your child has a problem, just trying harder is very unlikely to do any good.
There is another issue warranting attention. This discussion assumes your child has been in school and has been taught to read or at least has had an adequate educational experience to this point in his development. Unfortunately, this assumption is not justified in many communities and in many schools. Those schools do not adequately teach most children to read and the associated learning is sub-standard. If your child is having learning and especially reading problems, it may be he simply has not been taught to read and learn in school. Your child may not himself have any learning issues other than receiving inadequate instruction. If this is the source of your child’s difficulties, there is no simple solution short of your developing a compensatory learning program for your child. This likely includes competent tutoring either by you or a qualified teacher. Your child’s school may improve; but by the time it does, your child will be past the age where it can help him. This problem is common enough that parents with children in U.S. public (and many private) schools might reasonably start with the assumption their children have not been adequately taught whenever they notice their children experiencing reading or learning issues, unless an alternative explanation is fairly obvious. Efforts to help their children can then proceed from that base.