Before Steven Colbert was running for President, Pat Paulsen sought the position. In his campaign, he had strong views on many thing. When Pat was asked why he opposed sex education in schools, he said, "Let the kids today learn it where we did - in the gutter." That was 1968, and I think it still is the prevailing idea of sex education. Good accurate information on sex is still not being presented to the children. The problem is that back then the reason for sex education was to prevent unwanted pregnancies. The common sexual transmitted diseases (STD) were basically curable, and, while it would be good to decrease the incidence of STD's, if they were identified early, antibiotics could be successfully use against them.
However, things have changed since the 1960's. There has been several STD's that are now around that not only can not be cured with antibiotics such as genital Herpes, and certain varieties of Gonorrhea are now resistant to the drugs available. Further, AIDS and Hepatitis C are incurable, and fatal. Sex has picked up a lot of problems.
The problem is that even with these changes, many have not changed their attitude towards sex education. The same objections are being presented against the teaching of the topic in schools. Many religious people feel that their children should only be taught "Abstinence". While it might be valid approach towards sexual activities, it does not prepare a young person for the possibility they will ever find themselves in a situation that is outside of their understanding. They are not ready for everything that life might present them. This is only inviting bad things to happen.