Just because someone is Mormon does not mean they stay moral. No one is moral. Many (Christians)subscribe to moral tenets but no one is capable of being moral. If you don't believe that our public schools promote promiscuity by what and how they teach you have your head in the sand. I see the results of public education and don't need to be sitting in the classroom.No it doesn't mean they stay moral. However *on average* the mormons I know are the most upright people I know. I can't have a beer with my Mormon friends, which is a bit depressing and I haven't seen Jesus running around North America either, but I still respect them.
I think girls and boys sitting in school together being taught sex education from an adult point of view leads them to search (movies,internet, etc.)and experiment. I agree that there are a number of things that lead to the promiscuity that we see. To say one is ranked higher than another is a tough call.