Just so you know, one categorical "don't do it" question on the Iowa Acceleration Scale is, "Would the skip put the child into a sibling's grade?" At the very least, it would weigh heavily against such a skip, unless the sibling skips, too. And that could make for a pretty chaotic household for the first few months? They suggest doing in-place accommodations instead of skipping if the skip would move the child into the same grade as a sibling.