Based on reality and hints in the book iI believe there was sex happening at Hogwarts. When Ginny walks in on Percy snogging his girlfriend it seems like he is overly embarrassed to just be caught kissing. So iI believe that while it wouldn't have been appropriate to actually talk about sex in her books based on readership she was alluding/ hintinghinting towards it.
Great point by Commusoft, The designers of Hogwarts at least expected the men to attempt to have sex with the women. Whether they were worried about it being forced or consensual is another matter...
