Bathroom sign out board for the classroom. One boy and one girl at a time max. Student writes their name and time on the board and takes the pass. When they come back, they erase their info and rehang the pass.
My elementary friends--this bathroom tracking sheet not only provides documentation, but it allows your students to practice telling time! I don't particularly like this format because it seems like it would waste so much paper and ink; I would create my own that's more eco-friendly.