I don't want you to walk away thinking you have to grade skip your DC5. Some if us have chosen to decline an offer to grade skip. Like some posters have already mentioned, so much depends on your specific child (level and areas of high cognitive ability, EQ, social maturity and savvy, physical development, teachers, administrators, GT curriculum, school, district, family dynamics and past experience of both the child and family members, etc.)
Grade skipping was brought up by DS13's first and second grade teachers. That would have been much easier for the school then SSA in math, which ultimately happened in 2nd grade. So DS was SSA into 3rd grade GT Math (compacted 3rd + 4th grade plus with more depth) when he was 7 and then Pre-Algebra when he was 9. He tested higher both times and could legitimately (without accomodations for writing and explaining work) have accelerated more both times but we all (DS, parent and school) chose not to maximize the accelerations after balancing all the other considerations. With every passing year, I am increasingly happier with our decision to not grade skip DS.
Some random considerations that I actually did not fully comprehend six years ago. There is an immense divide between garden variety gifted and extreme ability, particularly if your child has any interest in pursuing national competitions in math or science or even the arts. Many opportunites are by grade so you can potentially accelerate your child out of the interactions with intellectual peers. There are quite a few extremely high ability kids who do not grade skip. DS has had the good fortune to compete on math teams with and against some of them. I am talking about middle schoolers who are USAJMO or 9th graders who are already USAMO. DS is not at that level. However, there are many more kids around his less exalted level - for example, at his chapter mathcounts, easily half (more?) the kids qualifying for the Countdown round, including DS, were Part of JHU SET ( at least 700 SAT by 12). DS has perfect math scores and 99 percentile reading scores from the SAT a year ago and ACT earlier this year but he would not be competitive with his true intellectual peers if he were accelerated four years (to high school senior).
Speaking of SATs (or ACTs), I think it would be pretty easy for gifted kids to test college "ready" years early, especially if you ignore actual writing achievements. For example, DS easily scored well above average (unofficially and for curiosity) on both math and verbal (CR) on the SAT the first time he tried it at age nine. However, he clearly did not belong on a college campus for a variety of reasons.
