I hand you the Palin clan as a shining example that abstinence doesn't work for all teenage girls and boys.  It's not about whether parents "allow" or "don't allow" their teenager to have sex.  When hormones rage they rage.  Are you sure you didn't sneak a quick one when your parents weren't looking, Koestler?  Or how about your son or daughter?  I'm confident that if you are a parent you can't be with your child(ren) 24/7 to monitor their sexual activities.