Honestly, I'm not surprised.
Or will, considering the time frame
As far as I'm aware. She was fucking him early into their school years. So yes, they have been fucking already. This was just a none sex form of her sexually assaulting the guy, since she probably would have gone to wrap something else of his down their, if not for PE making it slightly more difficult to pull him to somewhere more private. Key word being "slightly", as I feel like there was a previous chapter during their school years where she just did it in the bush or somewhere with him during PE.