Also keep in mind that public schools need only to "consider" private testing. Depending upon your district this could mean "read" the testing and nothing more to fully implementing the recommendations to anywhere in between. Additionally, they will do their own testing to determine eligibility.
For this reason, if you would like the school to implement accommodations, support or related services of any kind, it would make sense to get the school evaluation going. If you disagree with the results for any reason, you are entitled to request an IEE - independent educational evaluation from an independent professional of your choice, providing they have the needed credentials.
If, as they are testing, they find snags in his skill areas, this would be important to know so that they can address the difficulties by presenting the tasks in different ways or perhaps adding supports so that he can be more successful. Perhaps with his SI difficulties, they could help him begin to self regulate so that he could function more easily. They could also add accommodations such as motor breaks, so that he can burn off steam. If he has difficulty following directions - it is important to understand why - is the APD? Weakness in certain areas or memory? Attention? Language processing? Impulsiveness? La Texican gives a great example of a strategy the school can use to overcome these difficulties. As he matures, he should be taught strategies he can use to help himself in these areas.
An evaluation can help you understand him better and figure out how to help him. If he qualifies for special ed and an IEP, it helps insure that the school is designing a learning program that will support him in ways that lets him capitalize on his gifts. Often without this, the child becomes negatively labeled: lazy, bad, uncooperative, etc.
I also find it hard to believe there are not good private evaluators in the SF area. I would contact the major universities in your area such as Stanford to get some names of local professionals. Ideally you can find someone that you will use throughout your child's educational career. Perhaps in the future you would need him or her to join you for a meeting at the school. Finding a local resource would help you in the long run.
