So are you saying that you would be moving back to the states after next year no matter what so that current 9th grader would be back in the former school? To me, that changes the story considerably because it sounds as if you would just be moving back early. Did you just get to Europe? I don’t think that being number 1 in current HS vs top 10% in excellent HS back home would make a difference. She can still put that she was #1 after junior year.
Why couldn’t she take some classes at the HS and then some AP classes online? Will other students be doing the same thing?
What about for you? Do you have a job option back “home”? Can you easily end your contract early?
I think she will be fine in admissions either way, as long as she continues to excel.
What about the experience of being abroad? I think that counts for a LOT and will add to the overall picture of the student much more than just a rank number.
Just a heads up… I did read on CC that some kids transferring to a new high school suffer greatly with recalculation of GPA. This may not apply to the school you are considering. You may want to reach out to the counselor and find out how this will potentially effect your child. I definitely read this about some high schools in Texas not weighting transfer grades and etc. This prevented some kids from getting into U of TX after transferring. This is only an example of a bad outcome. But there are so many aspects to such a big decision. You will figure out what is best for your particular situation.