It is certainly possible that he is simply a little behind in the reading readiness/phonics area. It is also possible that his struggles indicate a learning disability - that is the reason I suggested the evaluation. First graders' ability to concentrate is limited, but it generally suffices to grasp the reading process, a major goal of first grade. Motivation varies from child to child and can be hampered if a child is struggling and therefore does not find enjoyment/success in school.
I just want to know what about my question makes you think my son needs to be evaluated for a possible learning ability. How can you be so certain that he is not just immature? Is this a development issue, should he be able to concentrate and be motivated to learn by age 6? thanks.
I would not advise you to focus on the matter of motivation - that will likely not yield much fruit. I would suggest he be evaluated for a possible learning disability. In addition, you should notify his pediatrician about the afternoon fatigue. It may indicate a sleep disorder, and at the very least the doctor will want to order some routine lab work to rule out any metabolic or endocrine problem.