Many teachers I know have difficulty deciding how to monitor how often students are permitted to leave their classroom to retrieve forgotten homework, find their ID card, run to the bathroom or get a drink from the drinking fountain. I have come up with a system that works well for me: Boletos Gratuitos. At the beginning of each semester, I give each student three boletos printed on neon colored paper. They are to keep them in their classroom binder and have them in their possession each day. If they forget a pencil or need to leave the classroom for any reason (including if they are tardy for any reason) they quietly put their name and the date on the back of the boleto and turn it in to their class period's tray. If they run out of boletos they are no longer permitted to leave the classroom or if they must, then they are assigned a lunch detention. If they keep boletos all semester without needing to use them they can turn them in for one point of extra credit at the end!
I have been using these for the past two years, and it has really cut down on unnecessary running in and out of the classroom. What system do you use that holds students accountable for their classtime and yet still allows for mistakes?