Don't agree to it. I speak from bitter experience. My DS (now 19) told me that he was staying for an after school club when he was 14, and went to his girlfriend's house, instead. She was also 14. Her mother, at least, was at home - and allowed the two of them to not only go to her bedroom, but close the door...
Anyone who tells you that kids that age are incapable of having sex... pfft.
In my house, there was an open door policy - which my son knew about. His older sister (she's now 27) had the embarrassment as an 18 year old, with her first "proper" boyfriend visiting our home, of having her bedroom door propped wide open and me wandering past every now and then (household chores, using the bathroom). My son knew that the same would happen if he brought a girl home. I mean... I didn't engage in conversation, I just made sure my presence was known (which successfully cockblocked in my house).
To this day, I cannot fathom the mentality of the girl whom my son lost his virginity to's parents. I really can't. They were kids... I mean, even at 19, because of covid, my son is immature, but even back then, they were 14... and as the mother of a daughter, what the actual fuck is letting a hormone laden "let's try this" boy stay over (because yes; my son would have been just as into "ooh, body parts, how do they slot together...?" as the girl he was "dating" at the time was) going to do for her self-worth?
Not everyone parents the same way, sure - but when we're dealing with hormone laden adolescents/teenagers... and it's the girl who stands to have her life derailed if she gets pregnant (because one way or the other, it has an impact), maybe we ought to grasp that 13/14/15/16 year old boys are sneaky buggers and tend to offload responsibility onto their parents, and just not allow our daughters to be put at risk.
(Just for the record, my son didn't knock the girl up - to the best of my knowledge - and nor did he contract an STI. In fact, she dumped him within a month because he wound up with a tumour that she felt distorted her SM image... again, another reason as to why kids this age ought not to be given the chance to slot body parts together! They're children themselves.)