There was a time when University City Schools were at the forefront of Sex Ed. It has been awhile. And there have been a few state laws tossed in, because, well, there are some polititians who think 1875 was a pretty good year so why change. So, in Missouri, science cannot really be used to teach Human Sexuality. But, there is nothing tha says parents (hi!) cannot provide current (as of 2014), medically accurate information.
170.015, RSMo. Instruction--Materials and Subjects - Human sexuality and sexually transmitted diseases, instruction in, requirements--policies, school boards' duties--certain course materials on human sexuality prohibited (will open in a new window)
Current SDUC Policy on Human Sexuality Education (will open in a new window)