I definitely believe that kids should learn about sex in school, but I do have reservations about some of the way that it is taught. Why do I think that it should be taught in school? Because people need to be exposed to an alternate viewpoint. Regardless of what is taught in the family (or not taught) or shown in the media (or not shown), there needs to be an availability of information (in an ideal world it would not be biased, but this is impossible) that is based on a curriculum that covers major points in sexual education, and directs students to resources that they could access (without fear or concern about how they would be perceived). Ideally, I think a such curriculum should be crafted with both librarians (to ensure depth and breadth) and teachers (to ensure appropriate pedagogy) working in tandem.
Of course I still have qualms with how individual instructors take up the cause or are forced to teach this material, however I do believe it essential to our collective educations.