Apparently "about 35% (of federally funded sex ed programs in public schools) not only required abstinence to be covered but either did not allow discussion of contraceptives or allowed discussion only of their failure rates".

http://www.avert.org/abstinence.htm


And apparently scientific studies have been done. The above link mentions some of them, and the AMA has come out saying that it cannot support abstinence-based sex ed programs...

http://www.foxnews.com/story/0,2933,140823,00.html


According to this AIDS prevention website, the Texas Department of State Health Services conducted a scientific study and found abstinence-based sex ed programs to be ineffective...

http://aidsblog.blogspot.com/2005/02/abstinence-based-sex-education-fails.html


This is what the Union of Concerned Scientists has to say about it...

http://www.ucsusa.org/scientific_integrity/abuses_of_science/case_studies_and_evidence/abstinence-only-education.html


This paper discusses the body of scientific work that has been done on this subject...

Abstinence Only vs. Comprehensive Sex Education