Tapas has its own hazy guidelines on this, which people who've been here longer than I have are better placed to advise on, so I'm going to answer the question more broadly.
I really like sex scenes in novels. I always have. So long as they're well written, they can be as detailed or as vague as the author likes to write them. I like delving into that depth, emotion, and vulnerability of a character.
Ahem. BACK IN MY DAY, young adult fiction had a LOT more sex in it. None of this fade-to-black nonsense either, it was detailed stuff. I think my high school librarians would have turned purple at some of what was in those books, and they were just sitting there on the shelf, no 'senior students only' labels on them, no 'special shelf' behind a locked door. And honestly, this was ideal. A well-handled sex scene in a YA book is a very healthy way for a younger person to explore that aspect of themselves. It's certainly more safe and advisable than, uh, 'learning' it from their peers.
I really hate the fact that YA lit has drifted into, and kind of merged with, the upper range of kidlit. I can only imagine the Twitter storm which would ensue, were a prominent author to write a sex scene which didn't fade to black between two underage characters. Common sense and Romeo and Juliet laws be damned. It's grandma-level puritanical. Not to mention, denial of an uncomfortable reality which teens will find other, far less safe, 'outlets' for.