Posting some rolling admissions schools to consider for those who don’t have any high school boarding school admissions at the moment:
Some rolling admissions schools that come to mind:
Cheshire Academy
Canterbury
Gunn
Williston
Trinity-Pawling
Avon Old Farms
Dublin
Proctor
Salisbury
In addition, one can consider applying to junior boarding schools that are 6-9 or K-9, for 9th grade. The JBSs lose a lot of kids after 8th grade, so they often have space for 9th grade. Admissions for 9th would not be overly competitive if they have space, and is potentially a great way to prepare to re-apply to HS BS next year for 9th or 10th grade.