She barely knows what the class is about. The teacher has been up front, and damn the man has some energy, and all she can do is fantasize about him. With a little grin to herself she decides to see what he'll do.
Sitting in the back has the advantage that he's the only one that can see her. Throughout the class she starts teasing. Legs opened under the desk so he can see up her skirt. A flash of her bra here, a wink and blown kiss there. He takes note of it without stopping his flow. She notices a bulge in his pants. That just eggs her on, becoming more bold. A flash of breast and nipple, a nipple pinch and sex face, a grin as she pulls her panties to the side, petting her wetness for him.