One of the biggest talking points of those opposed to comprehensive sexual education in schools is the assertion that such things are up to the parents. After all, they're the ones responsible for raising their kid to become a productive member of society, they should supply the majority of input that their children receive.
That's all well and good in a world where everyone is either A). Knowledgeable enough to speak intelligently on the subject, or B). Dedicated enough to acquire the knowledge they need to speak intelligently on the subject; AND ALSO C). Willing to broach the subject. This is not the case, or to put it more bluntly; have you SEEN the teen pregnancy rates in the United States? SPOILER ALERT: We're number one. This is not a good thing. At least we're number two here.
It's pretty clear that American parents are (largely) incompetent when it comes to promoting sexual well being among their children. This is a topic that many of them have proven that they cannot be trusted to handle and thus schools have at least partially taken over.
And really, sex is no different than math or English or history, or a number of other things very few parents are qualified to teach. (This is kind of why we have schools in the first place.) While there are cultural differences in opinions on sex, there are cultural (and professional) differences in opinion on what math and English is necessary to be a productive member of society and what is absolute horseshit
What I'd like to do is shove a microphone in the faces of these parents that are so opposed to their kids learning about sex in schools and then ask them what they've taught their children about sex. Anyone that tells me "nothing" gets a tattoo that says 'ignorance-perpetuating moron' on their head. Because if you're complaining that it's your job to teach your kids about sex, and then not exercising the right to perform that task, you're a fucking idiot.