Collaboration Among Admissions Offices?

It’s a good question, often wondered about. The answer is no.

These schools will compete for students, and at times if they think they are unlikely to “get” a kid, they may simply reject the applicant even if the applicant is well qualified and would otherwise be admitted.

BS AOs sometimes speak to middle school secondary school counselors, and may ask whether Johnny or Jennifer is likely to attend if given an offer. Some parents or applicants will tell their counselors their top choices in hopes this kind of conversation occurs - this can also backfire, IMO.