I think children should be given comprehensive sex education, so they are equipped to make smart choices.
A number of parents, churches, and religious schools intentionally deny children the information they need to make wise decisions about sexuality, relationships, and reproduction. Many programmes limit access to information on birth control, for example, out of a misguided belief that ignorance will stop kids from having sex. In the worst programmes, children are given deliberate misinformation intended to frighten and confuse them, such as the lies that condoms are not a reliable method of birth control when used effectively, or that abortion causes breast cancer. Of course, these methods don't work. There is no appreciable statistical differences in the number of children choosing abstinence. Scaring and lying to children only makes them more vulnerable to lie, gossip, and exploitation - it does not prevent them from having sex, it usually just ensures the sex they have is more risky.
Although it may be upsetting to parents, young people do have sex and this is a normal part of life for many people. Threats and bullying designed to shame sexually active young people inevitably backfires, and that's not even touching on how utterly destructive those messages are to kids who have been molested or raped. Instead of dishonesty, being clear and honest with children is necessary to ensure they make wise choices and are also comfortable talking about the subject with trustworthy people in their lives. You don't want your kids learning about sex from movies, paedophiles, and inappropriate contentography, which is how I and my Christian school peers learned. You don't want your kids hiding symptoms of STDs, seeking DIY abortion, or running away because they are too scared to talk to parents, teachers, and church leaders about their desires or experiences; again, the experiences of many of my classmates. You can encourage abstinence without making those who are ready for sex feel dirty or humiliated. In fact, removing the shame, secrecy, and stigma from sex also seems to make it a lot easier to say no. When it becomes something you own and have personal responsibility for, rather than something dirty you have to sneak around to read about, many kids step up.