She doubles down on the humiliation

As you stammer to answer your chemistry teacher, you feel a pair of lips wrap around your cock and start sucking in what you desperately hope is another of Cecelia's illusions.

You though she could only use her powers on one person at a time, but if she could expand that to even invisibility against two people, you doubt she'd hesitate to suck you off in front of the class, as long as the teacher didn't see. Maybe even if he could. More immediately concerning, you can't stop your dick from getting hard and poking out of your boxers, to the laughter and cheers of the class. You can only cover your shame and hope the worst is over.