Here are some things I would suggest you could do.
If you have a reading specialist in your school or in your school district, I would suggest that you ask to have an academic assessment, to pinpoint exactly what level your son is reading at, and what specific areas he's having difficulty with. Ask for a parent debriefing after the assessment is done, so that you and the school can work together to help him.
If he's having difficulty figuring out how to pronounce words, then I suggest that you look at my website: www.dynamicreadingandwriting.com, to see if he has phonological awareness difficulties. This means that he's not hearing sounds clearly enough to help him match what he says to what he sees when he reads. This isn't a hearing difficulty, it's a perception difficulty, and there are ways to help children who have this problem.
If he can read his grade three words correctly, but doesn't understand the material, then I suggest that you make sketches of the material with him. That way he can organize, remember, and understand the information, using visual cues. We learn visually and verbally, but, if children are having difficulty understanding what words mean, then we can translate the words into pictures, and children get meaning that way.
Is there a resource teacher in the school your son attends? If he could have some in-school tutoring in his specific areas of weakness, that would be very helpful to him. If your school doesn't have a pull-out resource room, then perhaps you could secure a private tutor for him. Some school districts have Saturday classes for students who need help in specific areas, at a minimal cost. If this isn't available to you, then perhaps your school would know some retired teachers who may come to the school to help children, or who may tutor privately.
If that is the case, i can suggest to read for him some context. Then explain to him the importance of reading. Give him books to encourage him to read. Encourage him to use dictionary if there might be questions in the mind.
For students to become strong readers they must have strong decoding, fluency and comprehension skills in reading. The decoding is the most important of the 3. A student must learn to decode using the rules of the English language step by step. If a student misses this very crucial step to literacy he will not have the strategies to attack words in text that are unfamiliar to him. Fluency and comprehension usually follow as the decoding gets stronger. A student also needs to learn how to visualize while reading. Making pictures in the brain will help with the comprehension.
Go to your Doctor tell them..The school will not tell you if your son has Dyslexia look it up yourself I wish someone would have said something to me years ago ..the schools will lie...also there are site like YALE CENTER FOR DYSLEXIA AND CREATIVITY..great site..trust yourself...