Um - I would get him on Aleks.com and have him sign up as a 4th grader and let him see for himself. The assesment will get easier as he makes mistakes. Speed really isn't an issue right now, and these kids are amazingly intuitive about what they need. You can also give him a chart with all the multiplication tables on it, and let him refer to that. You just never know.
If he needs work at his current level, you can have him split his math time, but my son filled in lots of gaps while doing above level stuff.
Best Wishes,
Grinity
