Uh, flashing a class?? Are you referring to fellow students or students IN your class. If its your classroom, doesn't your desk have a modesty screen? You know, a solid front?? I kind of think that is why desks have those - to prevent 'between the knee' peeks.....

If its flashing other students - maybe you want to flash certain classmates j/k

Until you get that sporran, keep your knees together and pivot on the balls of your feet while sweeping the pleats and lowering yourself into your chair - just watch women who are wearing short skirts do it.....

And as far as looking girly - if you ever watch 'Tunes of Glory' - every single person that is wearing the kilt does the pleat sweep as they sit - you can always tuck/push the apron down in the center after you sit

Its not the action that is girly, but how you execute it!!! :P