Why are kids like this? (Blog/Rant)

I have noticed that kids are really aggressive in my school for no apparent reason. But its not kids being aggressive that really gets on my nerves, its more of the teachers. I have witnessed people getting bullied before and the teachers don't really do anything about it?? For ex: (This isn't really bulling but its still bad) Some random kid screamed the f-bomb (Fuck) At my friend and then she put up the middle finger at him during PE. The teacher was right behind him and said nothing. Yes, there might of been a chance that he scolded him after class. But the chances were very slim because most of the time I see it happen. My point is there are really nice and kind kids, and then there's shitty kids who skip class all the time. I just don't think its fair to the people who are getting bullied in my school. Because they say they will do something about it but they never end up doing so. :(