The only method in history ever proven to have resulted in significant populations remaining abstinent is extreme gender segregation.
If you live in a place where men and women are allowed to mingle with any hope of privacy, abstinence is an empty word.
Not that there's anything wrong with that, of course. Yes, there will always be a few who brag about remaining abstinent before marriage for religious reasons (which is, today, the only reason for it)....but even amongst those there're sure to be a significant percentage who aren't telling the truth.
In my view, this is the sort of thing that belongs in church, where it makes some sense. It makes no sense if you take religious principles out of the equation.