Possibly you don't have room for a giant mailbox center or funding...I have a solution for both. All you need is a crate and hanging files. I used to only use one crate, but with 36 chickadees the pack up line was never ending. So one crate is for boys and one crate is for girls. This also helps when papers go home, that are gender specific...soccer/volleyball/flag football/etc.
Papers that need to go home are in the tray next to the crates and then each student has their name on a hanging file. The filing team grabs and paper and puts in the matching folder.