Some children have a very difficult time learning letters or sight words at an automatic level. Most of the time, learning letter names and sight words is a visual task. Letters or words are presented and the child recalls them from memory. This is not a successful approach for all children.
What can you as a parent do? Engage the brain in alternate ways.
Try cutting a moderate grade sandpaper into 5”x8” cards and writing the letters or sight words on a single card each with a large, wide sharpie. Then present each card to the child and have him/her trace the letter or word with one finger. Have him repeat the name of the letter or word while he traces with his finger. This provides visual, auditory, tactile and kinesthetic input and increases the child’s ability to learn and recall the letter or word. When inventing new ways to engage the child’s senses think of anything which will stimulate the child’s sense of touch (the skin on his finger, for example) as well as the child’s engagement of his muscles (the tracing of letters), the use of sound (both the sound coming into his ears, and the creation of the sound in his mouth and vocal chords), and the use of his eyes.
Another cute idea is to get a small plate of sand (or salt) for the child to trace letters (or words) into. Fingerpaint is also a way to engage the child visually, kinesthetically, and tactilely. Singing songs or using commercially available learning tools which demonstrate the letter sound for your child, also work to engage the auditory parts of the brain.