A conversation with the head of the math department is in order. I know of some schools that are more rigid than others about which class an incoming student needs to take even if they’ve taken that math before. So us telling you “Choate has such and such math” won’t do any good if they insist that every incoming student takes choate’s particular pre calc class. Just a random example but start emailing math department heads! If you need an introduction email the admissions department and explain your questions. They should be happy to hook you up with the appropriate faculty member.