If I understand correctly, you are asking about SSA into 6th+ grade, while remaining in 5th as the home grade, not whole-grade acceleration into 6th?
This situation has not come up with my own children, but many years ago, two of my siblings were in this situation. It so happened, though, that the district had a cluster of buildings, including elem and middle, adjacent to the high school, separated only by an athletic field, so transportation was not an issue. Each of my sibs simply walked unaccompanied across the field to the other school. Which, now that I think about it, would probably not be acceptable in today's liability/school safety climate.
I hope others will be able to help with their more current experiences.
