I remember in high school, when we didn't have a teacher that day, my classmate brought something, so while we were waiting for our teacher, we played gambling with cards, like the game Lucky 9, where the number of cards increases.
We gambled our pockets in those days because, of course, we wanted to make money even though we were students. Now, the crazy thing you are talking about is that I don't remember ever having an experience like that.
Each has our own unforgotten memories and one of those are high school moments. So many things can happen during it. There is love life, got dropped out, and like the ones you said there, doing silly things when the teacher is not yet around but this can also be caused of being dropped out if one is not careful enough.
You guys are lucky to not get caught because I know gambling is highly prohibited in any schools as this is not a good example to the kids or students. Students are in tight budget so sometimes the stake involved can be their snacks or we will do our classmates a favour like do their assignments, something like that. It is risky but fun.