It is so frustrating when the school does not recognize your child's gifts, cannot reach/ teach him and ultimately begins the "blame game". I was in a similar situation, when ds was in kindergarten, he struggled with all table top activities and pre-reading skills. Finally we had he evaluated by the school and found out that he was indeed very bright, but he also had a constellation of deficits that caused him academic trouble. In 1st grade he began receiving reading a support services. It was a bit rocky, but he did begin to succeed more frequently. Fortunalty, he has always lucked out with outstanding, understanding teachers that "get" that he is bright and are willing to take the time to support his differences.

Based on your description, it sounds like your child should be evaluated. Even children enrolled in private schools MUST be evaluated by their home school district if the parents make a referral (this is covered by the child find provision in IDEA, Federal Special Ed law). An evaluation will help you to sort out his strengths and to begin to understand where he may have some struggles. Note, I say begin, because the process of understanding never ends as the child grows and develops and the demands change.

How do you do this? WRITE a letter to your district - the special ed director or director of student services if you can find the name, superintendent if you can't. State that you are concerned with your child's academic development and would like to have him tested in the follow areas:
Psychological
Educational
Speech and Language
(and maybe OT if he has fine motor/ handwriting difficulties)

The district MUST test within about 60 days (less in some states depending upon your laws). This site has a good example as well as other important info. If you are not in Massachusetts, just ignore the references to MA state law - everything else applies. http://www.concordspedpac.org/

You can find the sample letter on the left. Go to the section on testing/evaluations and it is halfway down.

Once your child is tested, the school will give you an evaluation report that includes test scores, analysis and recommendations. If the recommendations contain special services such as reading or writing instruction, you are entitled to this EVEN IF YOUR CHILD is in the private school. Sometimes scheduling can be difficult, but if you can make it work, it could be the way to go. The recommendations might also include accommodations. Things like preferential seating, check in's to determine if the student understands the directions, visual model of the task, check lists, more time, motor breaks - whatever is needed for the child to take advantage of instruction. If your school takes even one cent of federal money - THEY MUST IMPLEMENT accommodations under section 504 of ADA. The website I gave has info on 504 plans.

Don't delay. Information is power. Once you get the data and recommendations, you can begin insuring that your child has the supports and instructions needed to unleash his talents.

Best to luck - it can be worrisome but it can get better.