Here are bathroom passes you can use in your upper-elementary to high school classroom, called "Gotta Go Passes."
When students must really "gotta go," they give you one of their passes.
Students receive 3 of these passes each 9-weeks (I cut the paper longways and punch holes, so they can go in their binders). They can use them to go to the restroom or get water anytime during class. I encourage them to save their passes, however, and turn them in at the end of each quarter to earn extra credit points.
This is a really great management strategy I've used to limit the number of times students are leaving my classroom, and the extra points incentive is great, also!!
**NOTE: The thumbnail preview looks uneven. However, the actual product is correctly aligned.