Two comments on size-
1- a college with a med school, law school, b-school etc. (sometimes not even located in the same place as the college of arts and sciences) is going to have a deceptively large “enrollment”. There will be zero interaction with those grad students; they occupy different physical locations; unless a student takes advantage of the van/bus service to specifically go to one of those buildings, the enrollment won’t impact his/her experience at all.
2- My HS had aprox. 1150 students per grade, and we were all on the same physical campus. A college of that size has a completely different look and feel than a HS. Most high schools don’t offer 12 person seminars taught by two professors (I took one in college); most high schools don’t have weekly office hours where even a student in a 200 person lecture hall can have downtime with a professor asking for help or chatting about that week’s reading; most high schools don’t have a dedicated team of professionals who understand how to get hired by the Peace Corps, TFA, win a Truman/Fulbright, etc.
So encourage any HS kid who is worried about size (too big particularly) to spend time hanging out on a college campus to really experience what enrollment size means. My HS (very large) was on one city block and occupied the entire space with pathways and concrete between buildings and doorways. The green space was the football field behind the hulking buildings. There was one cafeteria which was always bedlam no matter the time of day. The library (not multiple libraries, archives, rare book collections,) was a cave-like place where you went to retrieve a book, not a place you’d want to sit in for any length of time, etc.
This is not what a big college campus is about! Some have botanical gardens; museums, beautifully manicured green spaces, gorgeous libraries, separate athletic facilities and recreation areas, acres and acres of land in addition to the developed portions of campus. Multiple food and commercial options. Separate buildings for sculpture, photography, dance, theater and music practice rooms. Labs- so many labs. My HS (at the time considered one of the best in the state) had four labs- one for bio, one for chem, one for physics, and one for the “new” computer science discipline. A similar sized college now is going to have psych labs with animals (and psych labs for human, not animal behavior studies), multiple spaces for all the other sciences.
My point? I’d encourage a kid to hang out at a few big colleges before using that as a screener. I was a Classics major at a U which at the time had over 7,000 total students (undergrad, grad) and a “large” class in my department would have been 40 students and held in a tiny lecture hall. A more typical class was held in a seminar room around a table.
Size is easy to determine (more so than cultural fit for sure) but not that helpful!