Try Googling 'What2Learn'. This is a tool which has thousands of interactive learning games and covers most subjects. There is lots for Math including multiplication and division so he may get a lot out of it.
It will record his scores so you can see how he is doing and has in-built rewards such as a virtual farm (completing learning games gives credits to spend on the farm).
Access is free but there are also premium accounts which are used to help fund the building of schools in developing countries.
