One place where you could assess his Math ability and get a really detailed report to show to the school is ALEKS.com (but the first grade they do is 3rd grade so you would need to think that he would do pretty decent in third grade math). And they assume you are a good reader, and if he wasn't a good reader you would need to sit with him at the computer and help him read.

...reading is pleasure, not just something teachers make you do in school.~B. Cleary