The Dutch norm is for parents to allow teenagers’ boyfriends/girlfriends to sleep over in their bedrooms. This would be shocking to most Americans. But it’s part of a more general attitude toward sex that emphasises the importance of autonomy, consent, communication, and avoidance of unwanted consequences. The result is very low rates of sexually transmitted diseases and teenage pregnancies, and a greater tendency for teen sex to take place within ongoing relationships rather than outside them. For more, see here and here.