The yield rates for the top boarding schools including PEA, PA, and Groton, are around 70%. Every year there are applicants getting off the waitlists of those schools. So you definitely have a chance. PEA has the most rigorous admission process so you won't be able to do much to affect their decision. For Groton, you can try additional reference letters from a trustee or current or past parents who could influence the admissions officers.
