One of the most successful implementations in a library was done in a low income high school in the Tacoma area. I had the amazing opportunity to interview the guy who ran it, and his story went like this- When he inherited the library from a kindly old librarian, it had become a place where students took naps. What he did was he moved the bookshelves out of the way, created a circular desk in the middle, and had four rows of computers, monitors facing him. He could see what information students were interacting with and if need be, police it, but he rarely had to.
Normally when I go to a library, I see a bunch of teenagers on facebook, youtube, etc. These kids were looking up blogs, wikipedia, etc. He explained that the first thing he did was integrate with the teachers, and ask if they wanted web quests, or similar web integration. He had a real talent for coming up with all sorts of cool online activities that could be easily integrated into a curriculum, and teachers were constantly giving him material to work with- if a student was struggling or wanted to do work on their own, he'd take them. This did mean a lot of extra work on his end, but the implementation was worth it. Not only was he getting students engaged with the material, he was helping students gain digital literacy.
I don't know how much you could take away from this for an elementary school library, but there's a lot to be said about finding cool online integration for whatever the teachers are working with- and that's huge. If you are in alignment with the teacher's curriculum, you'll have a much better chance of being successful. Also, the big thing he said he owed everything on was administration support, so best of luck with that side.