Me being a Sophomore in HS i see this all the time. I can see why you want to know. I personally don't sag , maybe a little but i don't go overboard like alot of people do. but that's it. In high school people are just trying to fit in. Alot of people say it comes from prison meaning i want to have a butt buddy, other people say this might be a sign of an alpha male in a gang. Another reason they sagged in prison was the lack of belts. They didn't want them to kill them self while serving in jail so they took them away. This dragged out into hip hop cultures over those years of it originating in jail. Young males saw rappers doing it and then the sagging culture was made. People say its gay to sag but its not. Gays do it, str8, bi, you name it. Teens in HS think of it as having swag or being cool. Some teens just do it to fit in. Point is, if you want to express your self by doing it go for it, just don't over do it. Just do it around friends or at school. I can see it being rude to do it at formal events but not with friends. Dont be discourage over what other people think of you. If you have any other question just shoot me a PM:).