There is a boy at my school who says these disgusting profane things all the time. It is very strange and annoying - should I tell my Principal?

If you feel that these comments are particularly inappropriate or offensive, then I would suggest telling a teacher about it. Just say that you feel uncomfortable sometimes with the things he says. Before you say anything, ask a couple of friends if they agree that his behaviour is wrong. This way, you can feel more confident if you tell a teacher, knowing that it is not just you, but also other people who disagree with his comments. You can use this to your advantage when telling a teacher. For example, you don't have to name the people, but you can say that 'some students' or 'several of us' have issues with what he is saying, or, if you ask, maybe some of your friends will come with you. If he is saying anything racist, homophobic, sexist, -basically anything that could be taken offensively or is particularly inappropriate in a school environment- or if he is targeting one person or a particular group of people, you definitely need to tell someone. It's a shame that there are immature people like that in the world. Good luck :)

Yes, you need tell the principal and get things taken care of.