I'd do a dress shirt and tie at the very least. Look at the pictures in the "dressy" but not "casual" or "formal" pictures thread. If the 'goal' look is polo and dockers, then ramp it up a notch with the kilt. And I'd make it a point to check in with the instructor.

I'd go in with a "I do have something to change into, but it's not half as nice as what I'm wearing....."

But whatever you do, don't blow your grade point over this. At least you can wear your kilt on a "non presentation" class day.

Edit - was typing when you posted - GMTA!