Thinking of possibilities

Delicious as Grace is, you're sure that you can't recover enough stamina to fuck her a third time, no matter how much she encourages you. You kiss her tenderly, stroking her lithe body as you look into her happy glowing face. Your mind considers future possibilities as she snuggles contentedly. She gives every appearance of infatuation, which while it has it's points could lead to serious complications. Her sister remains an unknown factor. Finally, you're well aware of the impropriety of fucking a student, your second in two days. This could not only put a final end to your career, it could result in legal consequences.

Long term solutions aside, you're keenly aware that you have to get Grace to leave. You guess that Brian has heard her orgasmic howls, unless he is still wrapped up in Valerie's body. While he's in no position to rat you out, having her come out of your bedroom, obviously well fucked, would only make clear what had happened. Besides all of that, you have a faculty meeting coming up and can't appear at that with the aroma of schoolgirl cunt on you. the key is to ease her out without upsetting her and causing her to make some angry error in judgement that could mess you both up.