Before moving to purely outside school supplementation, you may want to have a discussion with the school about the tiny progress and potential need for challenge. Proceed with caution in your approach as individual teachers respond in dramatically different ways (from delight and willingness to work out a solution to hostility). There is a great deal of advice on this forum about ways to advocate.
In general, though, it's not appropriate for a child to be spending math class reading a book. Unless, maybe, it's one from the Life of Fred series. ;-)
