That's another ill social phenomena that we have to deal with and try to fix. Kids should be told that there are things that should be done after passing the age limit, otherwise it will harm them physically. Of course, that's a criminal act, and the older partner should be properly investigated and punished, because a kid may not realize the consequences but adults do and they take the responsibility for that. EVEN if the kid initiates it and pushes for it, the adult should block that by any means.
I know my thoughts are too idealistic, but my point is that pedophills bear the full responsibility for that and they are the ones that just criminally punished!