In answer to the original post:
The decision to accelerate the first time was because we were moving from an accelerated learning program to a normal school in another state and DD was over a year above grade level in all subjects. We accelerated mid year in conjunction with the school change which is another natural break conducive to skipping.
The current decision to skip again is because a combination of curriculum compaction and SSA have DD over a year above grade level again and we were tired of the timetable juggle which SSA required. She is effectively only accelerating in English as she has met the requirements of the year above in other subjects.
I can't think of any other trade offs as it were. I can think of a few if we don't grade skip and that will include comprising DDs academic and psychological development for the sake of an artificial grouping based on age.
I agree that skipping students inappropriately could certainly lead to issues. Any decision has to be all about what is best for any individual child and made without projecting parental desires or fears into the decision process. That can be harder than you think as we are all a product of experiences that can colour our decisions.
While it is important that the child be on board with a skip be aware that their fears and concerns can be overwhelming and may mean that your clearer head has to prevail. Kids can't always see what is good for them. A trial period for any skip which has an exit strategy with no value judgement is important to allow everyone to see what can be achieved with support and care.
One other point although not exactly a trade off, you may need to be prepared for 'greater asynchrony'. Our DD is perfectly mature and indistinguishable from her peers who are two or three years older while in a public arena. At home she is allowed to be a little girl with her stuffed toys and cuddles and she can reread Roald Dahl or Captain Underpants if she wants. She is very aware that we are totally happy for her to be herself, whatever 'age' that is.
