Great way to keep students in class with incentivized bathroom passes!
Provide students with 1 set of 4 bathroom passes for each semester with the stipulation that these 4 passes are the only ones that will be issued for that semester. To keep students in class, allow them to turn in unused passes at he end of each semester in order to earn extra credit as a thank you.
I have found that this incentive works VERY well with secondary students. The key to the bathroom pass's success is consistency and staying true to the rule.