In some ways I agree with this because if their educated then they make an informed choice. Its not like you are going to stop teens from having sex, so at least teach them about pregnancy, AIDS and all that. I don't think it should be done at primary level though, secondary is good.
I like the idea that they are getting some education on relationships as we see a lot of unhealthy relationships as we grow up. With divorce rates being so high and spousal abuse now showing up in just boyfriend and girlfriend relationships I believe having a firm education and knowledge of what makes a relationship work may start to turn some of these trends downwards.
I believe that it should start in secondary school as well.