Tease her just a little bit with a gentle wind

Yep, you decide just to tease her a little bit. Humiliating her in front of everyone would be just too cruel.

You imagine a gentle wind coming from the outside, lifting her skirt up a little.

"Kyah!"

She drops her chalk, putting down her skirt with the other hand just in time before her undergarments are revealed.

"What might be the matter, Miss Anya?"

"N-nothing. Just... the wind is quite bothersome. May I ask for permission to close the window?"

"Sure. Go right on ahead."

Still holding her skirt with both of her hands, she walks slowly to the window. Then, carefully, she releases her right hand from her skirt to close the window down.

Unfortunately, just one arm isn't enough.

"Oooh!" she mumbles angrily.

She releases her other hand. Now, her skirt is completely **** to any kinds of attacks.

You can choose to send another gust of wind, this time lifting her skirt up for sure. Or you can play nice and let her close the window without any accident.