Well our DS7 skipped one grade and is subject accelareted another grade for math.
So far so good and half the year is over.
One thing to consiser is, what material will they be missing when they leave the classroom to go to this accelerated subject.
Also, will your kid be ok w/the older kids.
The kids are years older than my son so I was concerned.
At first he was too, he said he is shy to go. He told the teacher this and she was nice and told him , lets just try it out.

Ironically now during recess he says when he cries the 4th grade girls try to help me.
That is cute.
So , so far so good.