I remember my first all encompassing teenage love, I was 15 and he was 17.
His parents allowed us to sleep in the same room (I stayed with him every weekend as he lived 1.5 hours away) we holed ourselves up there most days and his parents just left us to it.
My mom knew I was at his house but she never spoke to me about sex, contraception or anything like that - it was all very taboo.
Looking back things did move quite quickly in a sexual manor...foreplay etc. He was my first ever sexual partner and although I didn’t feel pressured into it, I don’t think it would have happened if there had been restrictions on where we could hang out....I.e if I was allowed in his room but only with the door open, or if we hadn’t been allowed to share a room etc etc. Looking back in quite shocked how blasé his parents were about the fact he was probably sexually active (in some form) with a 15 year old.
I was 3 months shy of being 16 when we first met and we didn’t have penetrative sex until I reached the age of consent However - I was pregnant 6 weeks later.
I really wish I had been restricted in some way in terms of us being alone together because then our physical relationship probably would have been slower to develop.
I also wish my mom had spoken to me about sex and contraception etc but it was never going to happen.
You’re in a very difficult position OP, but having an older boyfriend whose parents hadn’t really cared what we were up to led to me going through some awful they affected me for many, many years.
15 years old is still a child and he needs to be aware of that and he needs to be aware of the true complexities of forming a sexual relationship with her.
I would clarify with him whether her parents allow him into her bedroom and what, if any, boundaries they have. I’d also have a very stern talk with him about contraception.