The people that cussed at my school always got hit in the back of their head...I had so many bruises there because I used to cuss so much :( XP Anyways, maybe because teachers aren't paid enough to stress over that stuff, and yelling at them would just waste time.
Cursing just isn't that big of a deal. Instead of saying "coitus" they say "f*ck". Instead of saying "feces" they say "sh!t". The truth is, kids are going to say these things, and unless you want to infringe on peoples' rights to express themselves, you should ignore them and move on with your life.