Learning to read is not primarily a function of intelligence.
Some children with low IQs learn to decode text easily. Others have great difficulty.
A National Institutes of Health funded study found that dyslexia is not tied to IQ.
The ease or difficulty of learning to decode text depends, for the most part, on phonological awareness.
If your child has an intellectual disability, a comprehensive reading assessment can identify his strengths, weaknesses, and what he needs in an effective reading instructional program. Whether they have high IQ scores or low IQ scores, children with great difficulty in learning to read stand to benefit from educational services to help them learn to read.
His progress may be slow.
He may need more direct, explicit instruction in vocabulary, verbal reasoning, and inferential thinking to understand what he reads.