Set up a situation that she could take advantage of

With a sensual look on her face, the dark skinned professor began quickly drafting the rule she wanted in order to have her way with a student she had had her eye on for a while. After finishing her ideas, she quickly wrote them onto a new page in the Rule Book, and with almost no effort at all her dreams were becoming reality.

New Rules:

During his Astronomy class tonight, Harry Potter will accidentally knock one of the advanced Astronomy telescopes off the Astronomy Tower.

Everyone bar Aurora Sinistra will acknowledge that detention every night for Harry Potter with Aurora Sinistra is a reasonable punishment for knocking a telescope off the Astronomy Tower.

Harry Potter will feel very bad about knocking a telescope off the Astronomy Tower and to make up for it will do whatever Aurora Sinistra asks of him during detention, no matter how he personally feels about it.

Harry Potter will accept whatever happens during his detentions with Aurora Sinistra as punishment for destroying the telescope and will not try to tell anyone about what happens during those detentions.

No one except Harry Potter and Aurora Sinistra will be able to find out what happens during Harry Potter's detentions with Aurora Sinistra.

Harry potter will not question why Aurora Sinistra writes in the Rule Book.

Levitating the parchment that she drafted her new rules on into the fireplace, Aurora smiled because now she set up a situation where she would be alone for hours at a time with Harry and no one would be able to find out what happens during their detentions, or even question that anything wrong was happening. Luckily for her, her next Astronomy class with Harry would be in just a few hours.