Hall passes
While there are some elements of American schools that can seem a bit more relaxed to outsiders, the concept of hall passes isn’t one of them. Sure, you might not have to wear a uniform, but you need written permission to be in the halls of your school during class.
Interestingly, more and more schools across the world are bringing in systems like this, mainly to stop students from asking to go to the toilet because they don’t want to do the task that’s been set. It is odd that we’ve got to the 21st century and we don’t respect another human being’s need to go to the bathroom, though.