Call me old fashioned, but I would never allow a kid, teenager or not, to watch that kind of trash. It does absolutely nothing to enhance their learning and growth experience. It could do a lot to encourage them toward aligning themselves with the lowest common denominator. Sorry, but I just don't see even much entertainment value in something that is so completely dependent on vulagarity and sleeze, regardless of the viewpoint being promoted.
I'm not a fan of South Park either. Nully, you (and your kids) need the influence of a conservative woman!