I don't believe it's a good idea for kids to have sex given the prevalence of teen pregnancies and sexually-transmitted diseases,

"it's not a good idea" is very, very different, from being illegal. Pineapple on pizza is not a good idea. It's not illegal, however.

not to mention the emotional trauma that can ensue from a break-up that often follows a too-young sexual affair.

Emotional trauma ensues from break ups no matter the age. But thanks again for your ageism.