As a teacher, I believe that there is a place for levity and “fun” in the classroom. However, it can’t be that way all the time, because then it would be day care. Most teachers that I know understand the value of both strict lecture and more freeing events, but it’s difficult to use “fun” learning activities if the students don’t behave during more structured classes.
High school students are a volatile group, and their attitudes can turn in an instant. Speaking for myself, I try to keep a more structured classroom until I get to know students. If they seem like a well-adjusted class, we can do more fun things. If, on the other hand, the class (or just one person in it) is disruptive, disrespectful, and immature, I keep a firmer reign on them.
It was most evident when I was teaching at both the junior high and the high school. Most of the high school students loved the class and thought I was goofy and funny. We played a lot of games and did not take ourselves too seriously. At the junior high, however, I ruled with an iron fist. The classroom rules were much more strenuous, and we did a lot more structured work. There was an occasion where a few of my Junior High school students were working with my high schoolers, and complaining about my teaching style and how I was so strict. My high school students were shocked, and came to me asking how I could be two different people.
Sorry this is so long. My advice, @rhector63, is to stop “pissing off” the teacher, and maybe class will become less serious.