OP, do you have any updates?
OP applied REA which is non-binding at least from the college’s perspective…they would not be backing out of anything. Perhaps the private high school had the family sign some type of agreement that REA would be binding, but I definitely question the ethics of limiting a student’s choices like that.
As there would be no way for OP to apply RD without the school’s cooperation (sending transcripts, uploading already written GC and teacher recs, etc.), the likely only recourse is for the parents to get involved.
IMO if the parents state the the student is uncertain about attending the REA school (which doesn’t have a decision deadline until May 1) should be enough to let this student submit more apps. That’s why schools have a May 1 deadline…so that students have time to grow (lots of growth senior year) and reflect on what they want in a college.
It actually incenses me that counselors put in these artificial and controlling rules, and if they are NACAC members, I would report them in a nano second because I expect limiting apps this way, while maybe not a clear violation of CEPP rules (but maybe it is), certainly violates the spirit of maximizing student choice.
Edited to add: under normal circumstances and rules, those admitted REA are allowed to apply ED2 elsewhere, as well as apply RD to as many schools as they want. Again: more choices = better outcomes for students.