My sister was the head instructor for an Abstinence Education program back a couple years ago, in which I was a forced volunteer. It actually lowered the pregnancy rate by 40% in the schools that she did teach this at. However, it really depends on the instructor, money, area, and technique. My sis had taught majority of it as "Abstinence Only", but showed some grusome photos of STD ridden genitalia
, had some teen moms & dads come in and talk, and a lawyer to talk to the guys about their duties financially as a "dad". But, she also did speak of using protection and etc.
I figure if you have the proper techinque and instructor it can succeed, if not, it's not going to work at all. But that's just my take.