Id have to go with Madinuk on this:
"IMO, mental readiness trumps calendar age."
If your son feels comfortable and wants to I highly recommend it. Chances are he will comprehend the math while being able to excel at it. At age 9 I was already reading high school level books in technology. While I did not understand all of it, what I did I enjoyed. And when time came, what I did not understand came easier to me latter "ahhh, I remember reading that. I did not get it but now it makes sense" To me that made it all the more fun.
Last edited by Edward; 11/17/16 04:09 AM.