They are essentially what would be in most US school districts high school freshmen. That's pretty young and they really shouldn't (if for no other reason that condoms can break, rarely), but according to a 2017 study that I've posted a link to before 20% of US 9th grade students have had sex with the next grades rising to 36%, 47%, and 57%.They both clearly want to and there's no logical reason why they shouldn't. I don't see why the story would improve based on whether they commit or not?
They're two teens in love, dating, clearly thinking sexually and are lying on each other while kissing on a couch. What does innocence mean here? Plus having sex doesn't mean you aren't innocent. Having said that, I imagine there will be an excuse that comes up.