I do second ColinsMum's point about staying where you are if things are going well. As for Middle School, I recently read the book "Doing School," which -- though it is a case study about a high school and thus has perhaps limited generalizability -- struck enough of a chord that it gives me a strong "gut" reaction against the "rat race" middle school. (And, actually, the one kid in the book who was staying true to the value of personal inquiry had been somewhat "innoculated" by going to a cool, project-based middle school.)
What do you want your kid to value? Getting good grades so they can get into a good school so they can get a good job, or being curious life-long learners -- which, I think will ultimately end up with the good job. The thing about "getting good grades" that bothers me is that it becomes too much about meeting the teacher/school's/standardized test's expectations, and not enough about, you know, actually learning.
I don't know enough about the "progressive" school to have an opinion about it. What is their educational philosophy? Do they have adequate resources? (I remember a cool little school near the town I used to live where the "librarian" had no library; he would come to the public library to check out stuff for the kids...)