Good times

You don't smoke on break. You get yourself excused during class and smoke then. On break the teachers are more likely to be out of the classrooms too. Also, when I was in high school we had 10 minutes between classes. It took at least 6 walking at a very fast pace to cross the campus. With 30 seconds tied up putting your stuff away from the last class that only leaves you 3 1/2 minutes to use the bathroom. If there were more than two people already in the bathroom you were out of luck.

When I was in high school you were dumb to ask to leave class and go smoke because the moment you walk back into class the first thing the teacher is going to smell is that you've been smoking. And there were over 3,000 students so there wasn't much chance of a teacher catching almost anything between classes

Assuming the teacher cared or you even got near the teacher when you came back to class. Most of the smokers I knew already smelled of smoke because they lived in homes with other smokers. A teacher would be hard pressed to prove anything without catching you red handed. What are they going to say? "Well I smelled my student before they left and they didn't smell like cigarettes but after they came back when I smelled them they did." I can just imagine how that conversation would go over. Probably starting with "You're smelling your students?" "Do you sniff all your students?" "Lets have a discussion about what behavior is considered appropriate around minors or anyone for that matter?"

Sorry