When it comes to weeding, a great starting point is to look at the last time items have been checked out -- for your library, running a few reports like you suggested (10 years, 5 years, and then 3 years) is a great idea to get a feel for how many items have been circulating.  Also, if you do a quick look around the library and pull the books are visibly not in good condition, that's a great visual tool for weeding.  Looking at how old the book is something to consider as well -- here's a suggested copyright guide specifically for school libraries based on the Dewey number:

  • 000 2-10 years (computer tech books may age faster)
  • 100 10 years
  • 200 2-10 years
  • 300 5-10 years
  • 400 10 years
  • 500 5-10 years (some science titles may age faster)
  • 600 5-10 years (technology titles may age faster)
  • 700 5-15 years
  • 800 Flexible
  • 900 5-10 years (country books, atlas, maps may age faster)
  • Biographies Flexible; 10 years for contemporary subjects
  • Encyclopedias 3-5 years (consider online versions)
  • Almanacs 3 years
  • Periodicals 3 years; 6 months if superseded by electronic resources
  • Fiction 10 years (you may want to keep award winners)
  • Audio & Video Check periodically for condition and content
Lastly, you'll want to make sure you have a discarding plan of action that's supported by the school (it might be in your circulation policy, so check there first).  That could be giving kids and teachers an opportunity to take the discards or even working with art teachers to see if the materials could be used in the classroom.  Or opening up donations to families -- I've seen carts of discards available at after-school events or open houses, but that was before COVID.  It's better to have everyone on the same page -- we've seen some recent PR disasters when schools toss books into the dumpster and the community is caught off guard (not that you can't do that -- if you have something that's torn or moldy or smelly, feel free to toss away!!).  Another option is to contact other nearby school and public libraries to see if they would be interested in books for crafts or if a Friends group would take them for a book sale.  Just make sure you talk to your counterparts and your school or city administration first to see if they have ideas on discarding and to see if there's language already in place to handle this.