Is there a school psychologist employed by this boy's school? As pointed out, by the other poster they might be able to shed some light on the situation. Its not rare for bright children to be bored or unmotivated by material and exercises that they have already mastered.
I agree with Rock Rose, that in the recent past many mommies taught their children at home in lieu of preschool or in conjuntion with it. I am teaching my 4 year old almost 5 year old at home. I use a kindergarten readiness guide and I do alot of talking and reading with him. He has learned alot of academic things from me. Seems like alot of moms I know would rather depend on a preschool to teach thier children. Pre-schools are great for socialization and helping a child adapt to a school-like routine to ready them for preschool but I don't want to depend on them exclusively, most of that is my job and its a real joy to watch them learn!
Zoejohn - are you this boy's grandparent? I'm just trying to get a picture of what's going on here with him, you refer to the parents in the "third person" so I'm assuming you're not the father? Are you his with the private kindergarten?
First, it sounds like he was skipped past children his own age and is in a class with children who are all at least year older (and some, 2 years older because they were held back a year before starting school)? "Almost 5" is too young to be in a class with "almost 7" year olds. That's too young.
He sounds like a bright little boy who, at home, picks up on his mother's schooling. I will say that ALL my three boys were reading before they entered kindergarten, and so was almost every other kid in their kindergarten class - because they were worked with at home, and they have mommies who play board games and read and write and draw and talk to them all day long. That's the thing about little kids - they're really BRIGHT, and the reason some kids aren't reading at the age of 4 is simply because no one taught them how. This boy seems bright in both writing and math, which is a great thing, and looks great for his future.
But he's too young to be where he is. He's out-competed by his peers, because he so immature.
Do you have the option to put him in public kindergarten next year, with his age peers, and with a teacher who understands that brighter kids must do more on assignments? (If the assignment is to write the first letter of a word in a picture, you try to write the whole word).
Best wishes. Sounds like he'll turn out great.
My almost 5-year-old son is not THAT bright but I do see traces of the same pattern you are describing. He is excited about everything he does but when it comes to work sheets, it took only a short while in preschool and JK until he questioned why on earth he should do them. Sometimes he refused to go to Kindergarten saying he was so bored even though he loves being with his best friends. Together with the teachers I made an arrangement that he would be given slightly different work and homework that skips most of the coloring and any dull repetitive jobs but gives him more problem solving or conceptual or math tasks. He truly enjoys it now and I am grateful that the teachers went the extra step. He has always been fast in grasping concepts and also been immune to being bribed or motivated with sticker charts and the like. Now, when he does some of the regular "boring" work sheets, it is a gesture to be nice to his teachers. Sorry for yapping away about my own son - just wanted to point out that it seems to me that you should look further into the way your son learns and which type of learning excites him and take it from there. It amazes me that he is already in a private school setting and they have not been able to find a way. If he does not get excited about anything anymore recently, I wonder if a child psychologist could also shed some light on the situation. Maybe he is going through a phase where he needs to withdraw from any expectations or may be closing up for other reasons. Good luck, sorry, no great advice.