A 1 yr skip worked for a year for DD9. Ok, it didn't really work for the whole year, but with some pushing of the teacher we were able to make it work for a year. However, the pacing was still the issue and if your kid is anything like mine, it sometimes seems like simply sitting in a classroom increases their base knowledge of stuff that is not being taught - it is almost like osmosis - knowledge is in the air and she breathes it in. So the pace of things becomes more of an issue as the year goes on.
We ended up homeschooling this year with radical acceleration to grade 6 and then she started part time in a school in gr 6 in January.Even this isn't where she needs to be, but she is a very social kid and needs the interactions with others, and we have not been able to find a homeschool group that she and DH fit in with.