This creates anxiety, which is responsible for the angry outbursts your son is displaying at this time. It is possible that your son hates to do this work with you because he doesn't grasp it, and doesn't want you to know. And that is his perogative. When a child is uncomfortable, learning of this nature is for the school to handle. There are many different ways to teach a child who learns differently from other children.
Some children learn to read by tracing letters in a sandbox.
Some have to hold letters in their hands in order to make sense of them. Some children need to learn by having sounds repeated to them over and over. The job of the school is to find out which method is most effective for each child, and to teach them, or recommend a specialist who can. My advice is for you to put away all the academic learning tools you have, and concentrate on the things that your son does well. Your son needs your approval right now, and your encouragement.