Masturbate to get hard.

"Er, ok," you say, and tentatively begin stroking your cock in front of the girls. As touch yourself, you notice a cute blonde girl in the front of the class looking at intently at you as she takes furious notes. You can't help notice her amazing legs folded gracefully under her pleated skirt.

You get even harder as your eyes notice just the beginnings of some cleavage at the top of her checkered blouse, as she's pretty well endowed and seems to be leaning forward to get a better look. Waves of pleasure are increasing and spreading through your body, and your cock is rock hard now.

As you get more and more aroused your eyes are wandering all over the room. There's a little redhead with tiny but pert breasts, watching you nervously but with great interest. There's a girl with very long, very straight black hair who is smiling really beautifully as she watches you jack off. And out of the corner of your eye there is your friend Diana, pretending not to watch you, but still very obviously keeping track of your arousal.

You didn't know that being watched would be such a turn-on, but you feel your excitement building, and you start stroking yourself faster and faster.

Diana speaks up: "So you can see now that Joe is fully aroused. Not only is he hard and erect, but his penis is also getting a little redder. If he kept going at this rate, he'd probably orgasm, and then our class would be brought to a premature finish. Joe, why don't you slow down a bit. Girls, would anyone like to touch him and try doing what he's doing?