In ancient times, among the common people, the average age at which children entered puberty was 16~17. This is the origin of our notion of adulthood beginning at the age of 18, even though that isn't much of a distinctive developmental milestone anymore — it used to be a major milestone. When people develop sex drives, they become independent minded, and want to go out and make a families, and society recognized that in granting them the rights and responsibilities of adulthood. But with improvements in nutrition for the masses, especially in the more affluent nations, the average age of puberty is now 11.
In no respect has modern society directly addressed the issues raised by this. We now have a concept of an interim stage, between childhood and adulthood, known as adolescence. But we truly don't have a concept of adolescent sexuality. 11-year olds are in no position to be making life altering decisions concerning intimacy, and the best society has to offer for advice is, "Don't do that." Unfortunately, this leaves our children without the benefit of our guidance, when confronted with tough problems — so tough that even adults make mistakes. The consequences of failure can be devastating. Teenage pregnancies and social diseases leave indelible marks on those affected.
Worst of all, adolescents with over-active sex drives who are too sheltered sometimes become the prey of the adults who are "sheltering" them. And the emotional and psychological trauma of being abused by a trusted adult is at least as damaging as an unwanted pregnancy or a disease. The problems don't show up right away, and the symptoms are tough to spot. But an adolescent who develops an intimate bond with an adult tries to think and act like an adult, thereby forfeiting important development stages that cannot be recovered later — either the child faces the normal sequence of steadily-progressing challenges, or he/she skips the lessons and then spends the rest of his/her life compensating for the absence of those skills. The actual amount of damage is tough to measure, but it goes without saying that such situations must be considered extremely serious crimes against the adolescents. People at all ages need to bond with people of the same emotional age, so that they will get the mirroring from seeing a bit of themselves in their partners, and so that they can work through the problems together. For adults, discrepancies between emotional and biological ages can be significant. But for adolescents, such differences have not developed. Furthermore, while still in school, it's hard to relate to people who are not in the same grade. Thus the bonding should be only with people who are going through similar experiences, meaning the same grade. Anything outside of this should be considered a crime, and the more the discrepancy in ages, the more serious the crime.
We also believe that children entering puberty should be required to go through a childcare training program, in which they have to care for children every spare minute of their days, for an extended period, such as two weeks at a minimum. If they have children of their own, this will be their lives for the next 18 years. Most 11-year olds like the idea of having free time, and being able to go to the mall with their friends, or to ball games, and to be kids a lot of the time. They don't like the idea of having nothing but chores after school, and all weekend long. To actually understand the nature of the decisions that they might make in their intimate relationships, they need first-hand experiences. This is easy to provide, and what they need to learn is within reach for them. (Changing diapers, making bottles, shopping, cooking, and doing laundry isn't rocket science.) So this should be mandatory education for all adolescents (girls and boys).
Adolescents should also be required to demonstate proficiency in handling condoms.
Lastly, sex without a condom, outside of the context of a long-term relationship, should be prosecutable as wreckless endangerment. For adolescents, the penalty should be a year at a boarding school where they will not have the opportunity for such conduct, because of close supervision.