Do you mean a school library with real hardcover/softcover books , digital resources, artefacts et al??
I think Diigo lends itself to actually create a pretty nifty indexing database system. The cool thing is that the kids could then also remotely see what books or resources are available and will be able to access any online tagged resources, Only snag would b that they would not be able to see if it is available (like if it has been taken out) or not.
The teachers could even make book lists that could form part of the system and leave notes for the kids to respond to….
I will ask the rest of my library community what software they use….