Ask her what she wants

"Stacy, I want you to know that I'm happy to fuck whichever of your holes you'd most like," you tell her. You only want to be a good friend, after all.

Stacy chuckles, and shudders, as she rides you slowly. "I can take a hint, John. From your saying that you'd like to be lubed up, it doesn't take a genius to know you're really after my butt," she says.

"Well, I'm happy to fuck your pussy if you'd prefer that," you tell her as she rises and lowers herself on your lap.

Stacy smiles. "Don't worry, John. I want us to stay good friends, so I'd rather not start carrying your baby right now anyway. Maybe some other time. My butt feels pretty empty anyway," she says with a slight groan.

"Right, better get up then," you tell her. She rises, leaving your pole fantastically slippery. "Wow, Stacy, you're really ready for me. Right, turn around and lean over, you instruct her. Stacy obliges. Her breasts hanging out of her blouse in the middle of class, but Mrs. Susan doesn't seem to be paying you any attention at all for some reason.

You spread Stacy's butt cheeks, and then lower her down onto your massive erection. Stacy whimpers as you enter her. "Oh god, you're so big John," she whines softly. She doesn't quite make it down to your lap when she stops. "You're filling me right up," she says, in wonder.

You take her shoulders with your strong hands, and help to lift her up again, until finally she's established a sort of a rhythm. She seems a bit shaky on her feet, so you do the work, which is easy enough for you anyway. Stacy doesn't seem capable of speech any more, and just emits a gentle shaky whining noise as you have her plunge your cock in and out of her ass.

You cum. Gushes of your seed as you let out a deep moan, just after cumming into Stacy. She gives a loud moan.

"Stacy!" says Mrs. Susan, loudly. "I will ask you not to interrupt my class."

"I'm comminnnng," moans Stacy loudly.

"That's as may be, but you can do it quietly. I want you to see me after school," she says.

As Stacy collapses forward on her desk, and moans. "Great," she says.

The bell rings, and class ends. As you sit down, you pull out of your food friend's sphincter, letting a trail of semen dribble from her.

"I feel full of your cum," Stacy says. "It feels nice. I wish I didn't get so horny in the middle of Mrs. Susan's class, but I'm glad we could stay friends," she says, earnestly.

"Me too," you say, sincerely. You tuck yourself away, but not before catching glimpses of other girls in the class peeking.