Filthy Preppy Teens

Okay, so you know how sometimes at school, there are some students who dress in really nice clothes and seem to have a lot of money? That's what we call preppy teens.

Now, imagine if those preppy teens didn't take care of themselves or their things very well. Their clothes might be all dirty and messed up, and they might not clean their rooms or take showers very often. That's what we mean by "filthy."

So, "filthy preppy teens" are kids who dress fancy but don't take good care of themselves or their stuff. Does that make sense?