Raising a child doesn't end when they stop flying past their milestones as infants; the responsibility to educate and teach your child never ends, even when things might feel uncomfortable.
If the sole responsibility for teaching a child starts at home, why shouldn't it come full circle? Teaching your child about sex is not always a simple task, but it's hugely important. There are uncomfortable questions, difficult answers, and sometimes it takes a moment to figure out how to tell your child the truth without being too graphic. Tthat doesn't lessen the significance, though.
Oftentimes the first question asked by a child is, "Where to babies come from?". I have three daughters -- my oldest being almost seven years old. I recall her asking me this question a few years ago. I wasn't surprised by it since I was pregnant with her youngest sister at the time, and since she was reaching a point where she was interested in learning everything she could about the world, the question was relevant. Trust me, I didn't tell her about a stork! I took a moment to think about the most age appropriate way to help her understand, and I chose a garden reference. I explained that Mommy had a garden inside of her, and that Daddy had the seeds. It's Daddy's job to plant the seeds, and Mommy's job to make sure that the conditions are right for the baby to grow. This satisfied her curiosity for the time being, but other questions have been asked through the years since then, oftentimes causing me to pause a moment to consider what I should say.
Children have questions about all sorts of things, and if you're not there and available to answer them, they're still going to seek out an answer. Whether you're setting aside time to bring it up on your own, or are answering questions as they come, don't put it off. While it might be a little awkward, it should have the same importance as teaching them proper hygiene, household responsibilities, and making sure their homework is completed each night. Sex is an incredibly huge part of life, and a part of helping raise children into well rounded adults is teaching them about their anatomy, as well as about sexuality, diseases, contraceptives, and so forth, even if it makes you feel a little uncomfortable. You shouldn't be waiting for the school system to educate your children on this matter, because chances are, one of their friends has been doing it already, and you never know how accurate that information is.
No matter what you were taught, no matter how inaccurate the information was that you were given, teaching your children the truth allows them to have a fresh start and a new way of thinking. I know a lot of us have suffered some type of sexual issue, and it's difficult to separate yourself from that. Still, you have the chance to help your children understand the real truth, and hopefully not go through the same things you did. No matter what age your child is, there is age appropriate information you can give them, long before they start school. Sadly, there are children who have parents that aren't willing to talk about sex. Considering that situation, it's great that the school system is able to teach this topic. It's important to have a good understanding of how your body works, and if they're not learning at home, at least they're learning it in school.
Not everyone is sex (or sexuality) positive, and it's reflected in what they're teaching. Where can your children get the best and most accurate information? Right at home! Just always keep in mind that you should make things simple and easy to understand when they're young, and elaborate as they mature. It's never too early to teach them about their own anatomy. Also, long before they're in school, it's important that they know that their body should only be touched by certain people during certain times, and that it's always okay to speak up if they're uncomfortable.
Though it's the teacher's job to teach your child a variety of subjects, the foundation of their learning should always start at home; sex education included.