Many people believe that a child needs to go to their highest level of learning possible. That's a great educational perspective. But as a parent, I have additional perspectives and my goal is the overall health of my child. For her, I think allowing higher level math would actually cut down on her options, taking time away from other activities that she enjoys more, and probably killing her love for math.
YES. We have not pushed DS to the highest level of math he could accomplish, but have placed him enough ahead (2 yrs) that he's learning some as well as a place where the work is not overwhelming in quantity, and where the age and maturity gap with peers is conspicuous but not shocking.
I do not particularly want him in the high school building before he's more ready to handle the executive function things (remembering to turn in the HW...remembering to write down the HW... not leaving his musical instrument in the hall for a day or two...) that come with being there. For DS, a 2-year grade accel. in math is not perfect but has been an okay compromise.
Totally agree with MON: your DS should get full inclusion in instruction at whatever grade level you decide to put him in. One day a week makes him not fit anywhere and not be a part of any class. He should simply be a member of the class he's accelerated to, with all the same responsibilities.
DeeDee
