1) All kids should know the actual truth about how sex works before they reach the age where they can become pregnant or make someone else pregnant. The number of people who end up dealing with a pregnancy before they learn how that happens is unfortunately not zero.
2) All kids should know how best to protect against possible unwanted consequences of sex, like pregnancy and disease. They should be taught how to prepare, and they should also be taught what to do if they forget to prepare protection, the protection fails, or G-d forbid, they are assaulted. Plan B and post-exposure prophylaxis are things that they should be able to get if needed.
3) All kids should know that some people naturally become horny when their hormones get going, some people take a while to get there, and some people NEVER EVER get horny, and all of this is OK and fine and 100% normal for humans.
4) All kids should be taught–from birth onward–that they never have to let anyone touch them without their consent, and they are not allowed to touch other people without their consent. Yes this means you can’t spank your kids; yes this means you can’t make them kiss Grandma if they don’t want to; yes this means that you can’t act like unwanted pursuit of another child is cute because they’re 5, because in 10 years it will not be cute at all. It might even mean long discussions about why we agree to let doctors do things to us that hurt sometimes, and this is a pain in the ass, but sometimes good parenting is going to be a pain in the ass.