It's a library system shared between multiple schools. If it's similar to how this works in England (a friend is a teacher), an area that runs public schools -

It's a library system shared between multiple schools. If it's similar to how this works in England (a friend is a teacher), an area that runs public schools -- in England a county -- owns all the books. Schools can borrow e.g. 30 copies of MacBeth one year, and 30 copies of Hamlet the next year, if the teacher doesn't feel like teaching the same thing every year. They can also borrow 250 different books for 12 year olds, 250 for 13 year olds, etc, to put in the school library. These are gradually rotated between all the schools in the district.