I don't think you have got to that point yet. Even though the dean will tell you you need 20 points. You aren't expected to do that until near the end of the game. So the game still wants you to progress other parts of the story first.I progressed to where I needed the Intellect 20. I tried to use the Cheatmod menu that came with the game and it didn't work when I slide the bar to 20.
There is a Walkthrough pdf (Note: this PDF is not a proper step-by-step walkthrough) Starting on page 16 of that PDF, you'll see each sex partner in the game with the a list of objectives and events that occur for each of them. You need to progress different points on each of them at different points in the game depending on what's available. Early on you can do some Anna, Emily and Nurse objectives but not all of them. I know this is not a too helpful but it should do for now.