If sexual education is not taught in schools, the children will have to learn these topics either from their parents, or their close friends. Some parents do not feel comfortable talking about this topic, which forces some children to learn from their friends. They may obtain false information, or even information that may harm them. If this is taught in school, they can be taught the correct information.
Classes about safe sex and consequences should be taught in public schools, and that can help teenagers more knowledgeable of what they want to do, and that can help them more preventive to unwanted consequences such as pregnancy, diseases, raising child, etc. Sex education can also be taught to parents as it helps parents understand what is happening to their children, and how to talk with them about that matter.
I think it is a no-brainer that sex education is a necessity in all levels of schooling because it helps develop a more mature citizenry. Individuals learn early the pitfalls and diseases that one can catch by having sex too early or with too many partners. It is important that it is taught in schools.
Quality, honest sex education in public schools should be taught because I believe the health of society greatly correlates to its sexual health. With proper sex education, unwanted pregnancies and sexually-transmitted diseases are more likely to be prevented than without the education. A lack of sex education, or poor sex education, only compounds problems in society.