...she'd miss the big 5th grade overnight trip. I'm more concerned I guess with a very petite little bookworm in the big halls, full time, with older and more "worldly" kids.
My first thought about this problem is to ask if she can go on the trip with her former classmates. Maybe you can make some kind of deal so that she gets her assignments done.
It's looking like my DS9 will go to middle school in September, so I'm asking some of the same questions you are. I don't think the academics will be an issue and am hoping that he'll fit in socially. There are 2-3 boys who are ten at the school and it goes through grade 12, so he'll grow into the age groups in a year or two.
I've been thinking about "least-worst" options lately and how difficult it is to find a challenging environment that also provides friends. It's not easy. Well, it's almost impossible.
If your DD is in a public school district, all her friends will move to the middle school in a year anyway, and she'll be able to eat lunch with them and hang around with them during free time.
It's not easy! I don't know if I've been of any help...but you're not alone.
Val