A potent spell combo.

"I know a spell that will do the trick...but I think I'll need a second one too."

You summon your magic and cast the first spell.

The fans in her hand suddenly turn completely transparent, allowing free view of her ass now.
The crowd in class starts to murmur at the change, so you act quickly.

You cast the second spell!

Yiantra is confused when she looks back at the Class and then at the fan.
She doesn't see that anything has changed.

She shrugs and resumes her work.

"So you made the fans transparent," your companion asks.
"More than that- anything she holds in her hands now will turn transparent. So if she piles up some cloth to hide her shame..."
"It will do nothing."
"Exactly," you reply, "The other spell is a bit of hypnosis. It basically means that she can't see the changes made. Think of it like a mental block."

Observing the rest of the Class, she is confused by the Students reacting like they see past the fan, but keeps up the now-futile act.

"That deals with her for a while. Now what about the others?"