I have a couple of questions for you...
Where does he go to school?
How is the teacher making things captivation?
Depending on the answers to those questions would help me with some insight....I have 3 boys and 1 girl....my boys do not sit still all! They learn more by movement and through story telling. Knowing that he is only 5.... it is priceless that he is daydreaming!! I wish I could do that !!!!!
My kids all go to a Montessori school in Phx called Villa Montessori. The classrooms do not have desks. The kids do have to move while doing work. That is part of the learning.
Along with what style of learning does he have? visual? auditory? or kinnetic?(sp?) when you find this out and the teacher taps into his gifts, he will do well. But remember he is young and sitting still and having to learn how to write could be boring to a 5 year old boy!
Just some things to think about and by no means am I an expert, but I do know that boys do not like to sit still and focus on fine motor skills until their bodies have had some movement! also look up Brain Gym....Google it and there are some exercizes that you and the teacher can do to promote focus! The work needs to be FUN and not just BUSY work to keep their attention!