There is the possibility that by letting him opt out, you'll teach your son that he doesn't have to do things he doesn't like doing. Not necessarily a good lesson, IMO.
I don't really understand this resistance to the Common Core, especially the math component. I've never seen threads here discussing opting out of other standardized tests, and don't see why this test is different, apart from what I suspect is a fake ground-roots movement against the CC that probably has a lot of unsavory weight behind it at its foundation.
