I was skipped. It was not my idea and I was given only a day to decide. I did not really want to be skipped, but did not have time to think it through. I didn't want to cause problems, so I agreed. I HATED it. I lost the friends I had in the old class and I was not able to make new friends in my new class for several years. By high school, things were better, but I am not sure what I gained by being skipped; I know what I lost.
My limited experience is that there are social consquences for girls who have good friends in their current grade. It can be really painful to skip and can take years to recover socially.