Debbie,
I checked ALEKS online, for my daughter who is in 4 grade. She loved it. And while she is not a "mathematical genius" , her teacher was indicating to me during P/T conference that she belongs to a group of kids in her class that are more advanced mathematically /grasps problems easily. I suggested Aleks online pull out sessions for those kids and she is running it through the principal to check if it is aligned with Utah curriculum (end of level testing they worry so much about due to NCLB!).
ALEKS, when purchased through the school, is only $35 a year , as compared to $19.99 /month when purchased privately. I hope the principal sees the value of it ! And there is no need to hire an extra teacher.
Aleks starts with a third grade curriculum, but if your son is advanced you can still test him online and see if he is ready. You can register for a 48 hour trial at no cost. Go to
www.aleks.com

Ania