Hello librarian hive mind!

I work with a local middle school/high school that is small and privately funded. They are struggling to set up their library because they don't have any librarians on staff and don't know where to start. I am putting together a list of recommendations to help them start the process, but I was wondering if anyone with experience has any advice? Maybe you have worked with a school like this before, or even have a small public library that you helped set up. In particular, I am interested in any ILS or similar resources that are free since I don't think they have a large budget. I realize there may not be a free ILS, but maybe you or a library you know uses something in place of an ILS that is free? Thanks for your suggestions! If anyone is interested, I can always summarize what I find out.