I would echo aeh’s sentiments that so much of what constitutes “fit” is dependent on the relationship between student and teacher(s). My DS9 is in a similar position to yours, and my decisions have been almost entirely guided based on his being enrolled with his core teacher. As we will hit an inflection point after the 2021/2 academic year, teacher flexibility and openness to individualize are top of mind in my calculus. (In my vernacular, flexibility involves more than superficial, assignment-level adjustments. For example, telescoping three years of math in one.)
A few questions:
Fit— Has your son attended any class visits? What has his reaction been to the student cohort and the teacher(s) with whom he would study? What did your class observations indicate? How has each school discussed individualizing your son’s instruction?
Pragmatics—What is/isn’t feasible for your family in terms of ability to homeschool in full or in part? What options exist for high school programs? Are any of these middle school pathways necessary to reach your target high school options?