HS Librarian needs perspective(?)

TL;DR - How do I differentiate between "bad" and "unknown" books in my weeding process?

Love being a part of this community! I am a HS librarian with a new-ish library (opened just after COVID, full renovation and all new books) with about 1500 books with a focus on high interest non-curricular reading - I like to claim I can find a book for every kid in my school to enjoy. My library was envisioned to be a resource area, the major resource being me - my background, flexibility, experience, and ability to relate with everyone in the building (I have lots of leeway to vet and get resources and pretty free hand as long as I stay within budget). I am not being (completely) self-aggrandizing to say I am one of the more vital people to the operation of the school. I am fairly proud of what I have been able to build over the past few years, and now I want to get even better.

Our collection is small and it is meant to be that way in order to grow. I have genrefied the library to better help students find books they will enjoy. The goal of my library is to encourage students to read books they like or that speak to them, as opposed to curricular books that they get in class. I have a good relationship with the rest of the faculty and we have a pretty strong reading initiative across the school. At any given time, I have 100+ books checked out (student pop. is 1400).

So to my issues, I have been running some stats on my books and I see that about 50% of my collection has NEVER been checked out and 90% have been checked out less than 10 times. I have been a teacher for more than 20 years and a Librarian for 6, and I realize, I have no perspective of what checkout statistics look like for literally any other library. I don't know if those numbers are expected or not. When I try to speak with other HS librarians in my local area (Philly suburbs) I find our jobs are vastly different, both in what they do and the scope of their physical collections.

So, other school librarians, how do you decide what books to weed out to make room for new or different books? How do you engage your school population to get them interested in books? Any other veteran insights to offer?