We have not grade-skipped, but we moved DD to a gifted magnet, and dealt with some fall-out. On reflection, I wish I had been more confident with my little "speech" when I explained my choice (even though I was not that confident). I think people saw my feelings of hesitation as the a-ok to attack. So...be firm and cheerful and suggest with your tone that you brook no opposition...even if you do have doubts.