Shrink her clothes

A simple clothes-shrinking spell should do the trick. It wouldn't take much for the shapely elf to start popping out of her suit. You wiggle your fingers, casting magical energy in her direction.

For a moment, nothing happens. Then, her skirt starts to ride up her strong purple thighs. Diamonds of skin appear between the buttons of her shirt as the fabric starts to strain. The elf blinks in confusion, slowly becoming aware that something strange is going on. She feels the breeze between her legs and grabs instinctively at the hem of her skirt.

She glances left and right, starting to looking nervous. The boys' basketball team are standing around watching her, grinning. She lets go of her skirt, not wanting to look flustered. It wouldn't do for an important official like her to lose face in front of a bunch of students.

"Work faster!" she barks at her assistant, who's struggling to undo the knots binding the naked cheerleaders to the wall. You tied them extra tight, of course. "This is unacceptable!"

A button pops off her shirt. She jumps, before making an effort to recover her composure. Her skirt is very short now, nudging at the hem of her panties and clearly delineating the curve of her very full bottom. She resists the urge to tug at it, not wanting to draw attention to herself, although from the expression on the boys' faces you can tell they know exactly what's going on. Another button pops, and you get a look at some juicy purple cleavage.

From the way she bites her lip you can tell that her bra-strap's just come undone, and she must be getting a hell of a wedgie from her slowly-shrinking panties. Goodbye, dignity. Hello, adoring public.